diff --git a/apps/backend/src/modules/catalog/controller.ts b/apps/backend/src/modules/catalog/controller.ts
index 408c212ec..86ca6ee1a 100644
--- a/apps/backend/src/modules/catalog/controller.ts
+++ b/apps/backend/src/modules/catalog/controller.ts
@@ -40,6 +40,7 @@ export interface CatalogQueryParams {
   filters?: {
     levels?: string[] | null;
     departments?: string[] | null;
+    subjects?: string[] | null;
     unitsMin?: number | null;
     unitsMax?: number | null;
     days?: number[] | null;
@@ -50,6 +51,7 @@ export interface CatalogQueryParams {
     breadths?: string[] | null;
     universityRequirements?: string[] | null;
     online?: boolean | null;
+    isDecal?: boolean | null;
   } | null;
   sortBy?: string | null;
   sortOrder?: string | null;
@@ -180,6 +182,15 @@ const applyInMemoryFilters = (
       return false;
     }
 
+    // Subject filter
+    if (
+      filters.subjects &&
+      filters.subjects.length > 0 &&
+      !filters.subjects.includes(item.subject ?? "")
+    ) {
+      return false;
+    }
+
     // Units range overlap
     if (filters.unitsMin != null || filters.unitsMax != null) {
       const min = filters.unitsMin ?? 0;
@@ -283,6 +294,14 @@ const applyInMemoryFilters = (
       return false;
     }
 
+    // DeCal filter
+    if (filters.isDecal === true && !item.decal?.title) {
+      return false;
+    }
+    if (filters.isDecal === false && item.decal?.title) {
+      return false;
+    }
+
     return true;
   });
 };
@@ -306,6 +325,11 @@ const buildFilterQuery = (
     query.academicOrganization = { $in: filters.departments };
   }
 
+  // Subject filter
+  if (filters.subjects && filters.subjects.length > 0) {
+    query.subject = { $in: filters.subjects };
+  }
+
   // Units range overlap
   if (filters.unitsMin != null || filters.unitsMax != null) {
     const min = filters.unitsMin ?? 0;
@@ -415,6 +439,15 @@ const buildFilterQuery = (
     query.primaryOnline = true;
   }
 
+  // DeCal filter
+  if (filters.isDecal === true) {
+    query["decal.title"] = { $exists: true, $ne: null };
+  } else if (filters.isDecal === false) {
+    appendAndCondition(query, {
+      $or: [{ "decal.title": { $exists: false } }, { "decal.title": null }],
+    });
+  }
+
   return query;
 };
 
@@ -465,6 +498,7 @@ export const getCatalogFilterOptions = async (
               name: "$academicOrganizationName",
             },
           },
+          subjects: { $addToSet: "$subject" },
           levels: { $addToSet: "$level" },
           gradingOptions: { $addToSet: "$gradingBasis" },
           breadthRequirements: { $addToSet: "$breadthRequirements" },
@@ -515,6 +549,10 @@ export const getCatalogFilterOptions = async (
       .sort((a: { name: string }, b: { name: string }) =>
         a.name.localeCompare(b.name)
       ),
+    subjects: (result?.subjects ?? [])
+      .filter(Boolean)
+      .sort()
+      .map((code: string) => ({ code, name: null })),
     levels: (result?.levels ?? []).filter(Boolean).sort(),
     gradingOptions: (result?.gradingOptions ?? []).filter(Boolean).sort(),
     breadthRequirements: breadths,
diff --git a/apps/backend/src/modules/catalog/typedefs/catalog.ts b/apps/backend/src/modules/catalog/typedefs/catalog.ts
index 67cc1c3f1..39fb1a802 100644
--- a/apps/backend/src/modules/catalog/typedefs/catalog.ts
+++ b/apps/backend/src/modules/catalog/typedefs/catalog.ts
@@ -22,6 +22,7 @@ export const catalogTypeDef = gql`
   input CatalogFilters {
     levels: [String!]
     departments: [String!]
+    subjects: [String!]
     unitsMin: Float
     unitsMax: Float
     days: [Int!]
@@ -32,6 +33,7 @@ export const catalogTypeDef = gql`
     breadths: [String!]
     universityRequirements: [String!]
     online: Boolean
+    isDecal: Boolean
   }
 
   type CatalogMeeting {
@@ -166,6 +168,11 @@ export const catalogTypeDef = gql`
     name: String!
   }
 
+  type CatalogSubject {
+    code: String!
+    name: String
+  }
+
   type CatalogTimeRange {
     minStartTime: String!
     maxEndTime: String!
@@ -173,6 +180,7 @@ export const catalogTypeDef = gql`
 
   type CatalogFilterOptions {
     departments: [CatalogDepartment!]!
+    subjects: [CatalogSubject!]!
     levels: [String!]!
     gradingOptions: [String!]!
     breadthRequirements: [String!]!
diff --git a/apps/frontend/src/components/ClassBrowser/Filters/index.tsx b/apps/frontend/src/components/ClassBrowser/Filters/index.tsx
index c8164c80c..2609fd1ee 100644
--- a/apps/frontend/src/components/ClassBrowser/Filters/index.tsx
+++ b/apps/frontend/src/components/ClassBrowser/Filters/index.tsx
@@ -10,6 +10,7 @@ import { sortByTermDescending } from "@/lib/classes";
 
 import {
   Day,
+  DecalFilter,
   EMPTY_DAYS,
   EnrollmentFilter,
   GradingFilter,
@@ -45,6 +46,10 @@ export default function Filters() {
     updateGradingFilters,
     enrollmentFilter,
     updateEnrollmentFilter,
+    decalFilter,
+    updateDecalFilter,
+    subjects,
+    updateSubjects,
     sortBy,
     reverse,
     effectiveOrder,
@@ -171,6 +176,15 @@ export default function Filters() {
     }));
   }, []);
 
+  const subjectOptions = useMemo<Option<string>[]>(
+    () =>
+      (filterOptions?.subjects ?? []).map((subj) => ({
+        value: subj.code,
+        label: subj.code,
+      })),
+    [filterOptions]
+  );
+
   const isClassLevelDisabled = Object.values(filteredLevels).every(
     (count) => count === 0
   );
@@ -206,6 +220,8 @@ export default function Filters() {
     updateTimeRange([null, null]);
     updateSortBy(SortBy.Relevance);
     updateEnrollmentFilter(null);
+    updateDecalFilter(DecalFilter.All);
+    updateSubjects([]);
   };
 
   return (
@@ -271,6 +287,22 @@ export default function Filters() {
             </IconButton>
           </div>
         </div>
+        <div className={styles.formControl}>
+          <p className={styles.label}>Department</p>
+          <Select<string>
+            multi
+            searchable
+            value={subjects}
+            placeholder="Select departments"
+            disabled={subjectOptions.length === 0}
+            onChange={(v) => {
+              if (Array.isArray(v)) updateSubjects(v);
+            }}
+            options={subjectOptions}
+            searchPlaceholder="Search departments..."
+            emptyMessage="No departments found."
+          />
+        </div>
         <div className={styles.formControl}>
           <p className={styles.label}>Class level</p>
           <Select
@@ -408,6 +440,17 @@ export default function Filters() {
             </div>
           </div>
         </div>
+        <div className={styles.formControl}>
+          <p className={styles.label}>DeCals</p>
+          <Select
+            value={decalFilter}
+            onChange={(value) => updateDecalFilter(value as DecalFilter)}
+            options={Object.values(DecalFilter).map((option) => ({
+              value: option,
+              label: option,
+            }))}
+          />
+        </div>
       </div>
     </div>
   );
diff --git a/apps/frontend/src/components/ClassBrowser/browser.ts b/apps/frontend/src/components/ClassBrowser/browser.ts
index 1f4084520..5719cb0b2 100644
--- a/apps/frontend/src/components/ClassBrowser/browser.ts
+++ b/apps/frontend/src/components/ClassBrowser/browser.ts
@@ -70,3 +70,9 @@ export enum EnrollmentFilter {
   OpenApartFromReserved = "Non-reserved Open Seats",
   WaitlistOpen = "Open Seats or Open Waitlist",
 }
+
+export enum DecalFilter {
+  All = "All",
+  OnlyDecals = "Only DeCals",
+  Hide = "Hide",
+}
diff --git a/apps/frontend/src/components/ClassBrowser/context/FilterContext.ts b/apps/frontend/src/components/ClassBrowser/context/FilterContext.ts
index 64cf5b152..2d9551a27 100644
--- a/apps/frontend/src/components/ClassBrowser/context/FilterContext.ts
+++ b/apps/frontend/src/components/ClassBrowser/context/FilterContext.ts
@@ -6,6 +6,7 @@ import { Semester } from "@/lib/generated/graphql";
 
 import {
   Day,
+  DecalFilter,
   EnrollmentFilter,
   GradingFilter,
   Level,
@@ -30,6 +31,8 @@ export interface FilterContextType {
   effectiveOrder: "asc" | "desc";
   enrollmentFilter: EnrollmentFilter | null;
   online: boolean;
+  decalFilter: DecalFilter;
+  subjects: string[];
   filterOptions: ICatalogFilterOptions | null;
   updateUnits: Dispatch<UnitRange>;
   updateLevels: Dispatch<Level[]>;
@@ -41,6 +44,8 @@ export interface FilterContextType {
   updateSortBy: Dispatch<SortBy>;
   updateEnrollmentFilter: Dispatch<EnrollmentFilter | null>;
   updateOnline: Dispatch<boolean>;
+  updateDecalFilter: Dispatch<DecalFilter>;
+  updateSubjects: Dispatch<string[]>;
   updateReverse: Dispatch<SetStateAction<boolean>>;
 }
 
diff --git a/apps/frontend/src/components/ClassBrowser/hooks/useCatalogBrowser.ts b/apps/frontend/src/components/ClassBrowser/hooks/useCatalogBrowser.ts
index 58df95d1c..39c88c9f0 100644
--- a/apps/frontend/src/components/ClassBrowser/hooks/useCatalogBrowser.ts
+++ b/apps/frontend/src/components/ClassBrowser/hooks/useCatalogBrowser.ts
@@ -58,6 +58,8 @@ export default function useCatalogBrowser({
       effectiveOrder: filterState.effectiveOrder,
       enrollmentFilter: filterState.enrollmentFilter,
       online: filterState.online,
+      decalFilter: filterState.decalFilter,
+      subjects: filterState.subjects,
       filterOptions: queryResult.filterOptions,
       updateUnits: filterState.updateUnits,
       updateLevels: filterState.updateLevels,
@@ -69,6 +71,8 @@ export default function useCatalogBrowser({
       updateSortBy: filterState.updateSortBy,
       updateEnrollmentFilter: filterState.updateEnrollmentFilter,
       updateOnline: filterState.updateOnline,
+      updateDecalFilter: filterState.updateDecalFilter,
+      updateSubjects: filterState.updateSubjects,
       updateReverse: filterState.updateReverse,
     }),
     [year, semester, terms, filterState, queryResult.filterOptions]
diff --git a/apps/frontend/src/components/ClassBrowser/hooks/useCatalogFilters.ts b/apps/frontend/src/components/ClassBrowser/hooks/useCatalogFilters.ts
index 9b9afec97..7502524c8 100644
--- a/apps/frontend/src/components/ClassBrowser/hooks/useCatalogFilters.ts
+++ b/apps/frontend/src/components/ClassBrowser/hooks/useCatalogFilters.ts
@@ -14,6 +14,7 @@ import type { GetCatalogSearchQueryVariables } from "@/lib/generated/graphql";
 
 import {
   Day,
+  DecalFilter,
   EnrollmentFilter,
   GradingFilter,
   Level,
@@ -117,6 +118,8 @@ export interface CatalogFilterState {
   effectiveOrder: "asc" | "desc";
   enrollmentFilter: EnrollmentFilter | null;
   online: boolean;
+  decalFilter: DecalFilter;
+  subjects: string[];
   hasActiveFilters: boolean;
   filterVariables: ICatalogFilters | undefined;
 }
@@ -133,6 +136,8 @@ export interface CatalogFilterUpdaters {
   updateSortBy: Dispatch<SortBy>;
   updateEnrollmentFilter: Dispatch<EnrollmentFilter | null>;
   updateOnline: Dispatch<boolean>;
+  updateDecalFilter: Dispatch<DecalFilter>;
+  updateSubjects: Dispatch<string[]>;
   updateReverse: Dispatch<SetStateAction<boolean>>;
 }
 
@@ -162,6 +167,10 @@ export default function useCatalogFilters({
   const [localEnrollmentFilter, setLocalEnrollmentFilter] =
     useState<EnrollmentFilter | null>(null);
   const [localOnline, setLocalOnline] = useState<boolean>(false);
+  const [localDecalFilter, setLocalDecalFilter] = useState<DecalFilter>(
+    DecalFilter.All
+  );
+  const [localSubjects, setLocalSubjects] = useState<string[]>([]);
 
   // Derive state from search params when persistent
   const query = localQuery;
@@ -281,6 +290,25 @@ export default function useCatalogFilters({
     [searchParams, localOnline, persistent]
   );
 
+  const decalFilter = useMemo(() => {
+    if (persistent) {
+      const param = searchParams.get("decalFilter");
+      if (param && Object.values(DecalFilter).includes(param as DecalFilter)) {
+        return param as DecalFilter;
+      }
+      return DecalFilter.All;
+    }
+    return localDecalFilter;
+  }, [searchParams, localDecalFilter, persistent]);
+
+  const subjects = useMemo(
+    () =>
+      persistent
+        ? (searchParams.get("subjects")?.split(",").filter(Boolean) ?? [])
+        : localSubjects,
+    [searchParams, localSubjects, persistent]
+  );
+
   // Build server-side filter variables
   const filterVariables = useMemo<ICatalogFilters | undefined>(() => {
     const filters: NonNullable<ICatalogFilters> = {};
@@ -310,6 +338,18 @@ export default function useCatalogFilters({
 
     if (online) filters.online = true;
 
+    // DeCal filter
+    if (decalFilter === DecalFilter.OnlyDecals) {
+      filters.isDecal = true;
+    } else if (decalFilter === DecalFilter.Hide) {
+      filters.isDecal = false;
+    }
+
+    // Subject filter (shown as "Department" in UI)
+    if (subjects.length > 0) {
+      filters.subjects = subjects;
+    }
+
     return Object.keys(filters).length > 0 ? filters : undefined;
   }, [
     levels,
@@ -321,6 +361,8 @@ export default function useCatalogFilters({
     breadths,
     universityRequirements,
     online,
+    decalFilter,
+    subjects,
   ]);
 
   const hasActiveFilters =
@@ -335,6 +377,8 @@ export default function useCatalogFilters({
     gradingFilters.length > 0 ||
     enrollmentFilter !== null ||
     online ||
+    decalFilter !== DecalFilter.All ||
+    subjects.length > 0 ||
     sortBy !== SortBy.Relevance;
 
   // URL sync updater helpers
@@ -431,6 +475,8 @@ export default function useCatalogFilters({
     effectiveOrder,
     enrollmentFilter,
     online,
+    decalFilter,
+    subjects,
     hasActiveFilters,
     filterVariables,
     // Updaters
@@ -459,6 +505,16 @@ export default function useCatalogFilters({
       setLocalEnrollmentFilter(filter);
     },
     updateOnline: (o) => updateBoolean("online", setLocalOnline, o),
+    updateDecalFilter: (filter) => {
+      if (persistent) {
+        if (filter === DecalFilter.All) searchParams.delete("decalFilter");
+        else searchParams.set("decalFilter", filter);
+        setSearchParams(searchParams);
+        return;
+      }
+      setLocalDecalFilter(filter);
+    },
+    updateSubjects: (s) => updateArray("subjects", setLocalSubjects, s),
     updateReverse: setLocalReverse,
   };
 }
diff --git a/apps/frontend/src/lib/api/catalog.ts b/apps/frontend/src/lib/api/catalog.ts
index 93edc5f8e..3667218e4 100644
--- a/apps/frontend/src/lib/api/catalog.ts
+++ b/apps/frontend/src/lib/api/catalog.ts
@@ -78,6 +78,9 @@ export const GET_CATALOG_FILTER_OPTIONS = gql`
       gradingOptions
       breadthRequirements
       universityRequirements
+      subjects {
+        code
+      }
       timeRange {
         minStartTime
         maxEndTime
diff --git a/packages/gql-typedefs/catalog.ts b/packages/gql-typedefs/catalog.ts
index 8ecfacc9c..cb6a80f43 100644
--- a/packages/gql-typedefs/catalog.ts
+++ b/packages/gql-typedefs/catalog.ts
@@ -22,6 +22,7 @@ export const catalogTypeDef = gql`
   input CatalogFilters {
     levels: [String!]
     departments: [String!]
+    subjects: [String!]
     unitsMin: Float
     unitsMax: Float
     days: [Int!]
@@ -32,6 +33,7 @@ export const catalogTypeDef = gql`
     breadths: [String!]
     universityRequirements: [String!]
     online: Boolean
+    isDecal: Boolean
   }
 
   type CatalogMeeting {
@@ -173,6 +175,11 @@ export const catalogTypeDef = gql`
     name: String!
   }
 
+  type CatalogSubject {
+    code: String!
+    name: String
+  }
+
   type CatalogTimeRange {
     minStartTime: String!
     maxEndTime: String!
@@ -180,6 +187,7 @@ export const catalogTypeDef = gql`
 
   type CatalogFilterOptions {
     departments: [CatalogDepartment!]!
+    subjects: [CatalogSubject!]!
     levels: [String!]!
     gradingOptions: [String!]!
     breadthRequirements: [String!]!