diff --git a/packages/trpc/src/utils/rescheduling-availability.ts b/packages/trpc/src/utils/rescheduling-availability.ts
new file mode 100644
index 00000000000000..d37a3074fa47ad
--- /dev/null
+++ b/packages/trpc/src/utils/rescheduling-availability.ts
@@ -0,0 +1,75 @@
+import { getAvailableSlots } from "@calcom/lib/availability";
+import { prisma } from "@calcom/prisma";
+import dayjs from "@calcom/lib/dayjs";
+import { EventType } from "@calcom/types/EventType";
+
+export interface ReschedulingAvailabilityParams {
+  hostUserId: number;
+  guestEmail: string;
+  eventType: EventType;
+  dateFrom: Date;
+  dateTo: Date;
+  timeZone: string;
+}
+
+/**
+ * Retrieves available slots for rescheduling considering both host and guest availability.
+ * If guest is not a Cal.com user, returns host's availability only (fallback to original behavior).
+ * Returns string[] of ISO 8601 timestamps (e.g., "2024-01-15T10:00:00.000Z")
+ */
+export async function getReschedulingAvailableSlots({
+  hostUserId,
+  guestEmail,
+  eventType,
+  dateFrom,
+  dateTo,
+  timeZone,
+}: ReschedulingAvailabilityParams): Promise<string[]> {
+  // Fetch host availability first (always needed)
+  let hostSlots: string[] = [];
+  try {
+    hostSlots = await getAvailableSlots({
+      userId: hostUserId,
+      dateFrom,
+      dateTo,
+      eventType,
+      timeZone,
+    });
+  } catch (error) {
+    console.error("Failed to fetch host availability:", error);
+    return [];
+  }
+
+  // Check if guest is a Cal.com user by email
+  const guestUser = await prisma.user.findUnique({
+    where: { email: guestEmail },
+    select: { id: true },
+  });
+
+  // If guest is not a Cal.com user, return host slots (original behavior)
+  if (!guestUser) {
+    return hostSlots;
+  }
+
+  // Guest is a Cal.com user: fetch their availability
+  let guestSlots: string[] = [];
+  try {
+    guestSlots = await getAvailableSlots({
+      userId: guestUser.id,
+      dateFrom,
+      dateTo,
+      eventType,
+      timeZone,
+    });
+  } catch (error) {
+    console.error("Failed to fetch guest availability:", error);
+    // If guest availability fetch fails, fallback to host slots (safer than blocking rescheduling)
+    return hostSlots;
+  }
+
+  // Intersect host and guest slots (only slots available for both)
+  const availableSet = new Set(guestSlots);
+  const intersectedSlots = hostSlots.filter((slot) => availableSet.has(slot));
+
+  return intersectedSlots;
+}
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