diff --git a/lib/openai/client.rb b/lib/openai/client.rb
index 6054af0f..313bfded 100644
--- a/lib/openai/client.rb
+++ b/lib/openai/client.rb
@@ -21,16 +21,16 @@ def initialize(config = {}, &faraday_middleware)
       @faraday_middleware = faraday_middleware
     end
 
-    def chat(parameters: {})
-      json_post(path: "/chat/completions", parameters: parameters)
+    def chat(parameters: {}, extra_headers: {})
+      json_post(path: "/chat/completions", parameters: parameters, extra_headers: extra_headers)
     end
 
-    def embeddings(parameters: {})
-      json_post(path: "/embeddings", parameters: parameters)
+    def embeddings(parameters: {}, extra_headers: {})
+      json_post(path: "/embeddings", parameters: parameters, extra_headers: extra_headers)
     end
 
-    def completions(parameters: {})
-      json_post(path: "/completions", parameters: parameters)
+    def completions(parameters: {}, extra_headers: {})
+      json_post(path: "/completions", parameters: parameters, extra_headers: extra_headers)
     end
 
     def audio
@@ -97,8 +97,8 @@ def realtime
       @realtime ||= OpenAI::Realtime.new(client: self)
     end
 
-    def moderations(parameters: {})
-      json_post(path: "/moderations", parameters: parameters)
+    def moderations(parameters: {}, extra_headers: {})
+      json_post(path: "/moderations", parameters: parameters, extra_headers: extra_headers)
     end
 
     def usage
diff --git a/lib/openai/http.rb b/lib/openai/http.rb
index 5459f64c..76107ea8 100644
--- a/lib/openai/http.rb
+++ b/lib/openai/http.rb
@@ -6,35 +6,35 @@ module OpenAI
   module HTTP
     include HTTPHeaders
 
-    def get(path:, parameters: nil)
+    def get(path:, parameters: nil, extra_headers: {})
       parse_json(conn.get(uri(path: path), parameters) do |req|
-        req.headers = headers
+        req.headers = headers.merge!(extra_headers)
       end&.body)
     end
 
-    def post(path:)
+    def post(path:, extra_headers: {})
       parse_json(conn.post(uri(path: path)) do |req|
-        req.headers = headers
+        req.headers = headers.merge!(extra_headers)
       end&.body)
     end
 
-    def json_post(path:, parameters:, query_parameters: {})
+    def json_post(path:, parameters:, query_parameters: {}, extra_headers: {})
       parse_json(conn.post(uri(path: path)) do |req|
-        configure_json_post_request(req, parameters)
+        configure_json_post_request(req, parameters, extra_headers: extra_headers)
         req.params = req.params.merge(query_parameters)
       end&.body)
     end
 
-    def multipart_post(path:, parameters: nil)
+    def multipart_post(path:, parameters: nil, extra_headers: {})
       parse_json(conn(multipart: true).post(uri(path: path)) do |req|
-        req.headers = headers.merge({ "Content-Type" => "multipart/form-data" })
+        req.headers = headers.merge("Content-Type" => "multipart/form-data").merge!(extra_headers)
         req.body = multipart_parameters(parameters)
       end&.body)
     end
 
-    def delete(path:)
+    def delete(path:, extra_headers: {})
       parse_json(conn.delete(uri(path: path)) do |req|
-        req.headers = headers
+        req.headers = headers.merge!(extra_headers)
       end&.body)
     end
 
@@ -95,7 +95,7 @@ def multipart_parameters(parameters)
       end
     end
 
-    def configure_json_post_request(req, parameters)
+    def configure_json_post_request(req, parameters, extra_headers: {})
       req_parameters = parameters.dup
 
       if parameters[:stream].respond_to?(:call)
@@ -105,7 +105,7 @@ def configure_json_post_request(req, parameters)
         raise ArgumentError, "The stream parameter must be a Proc or have a #call method"
       end
 
-      req.headers = headers
+      req.headers = headers.merge!(extra_headers)
       req.body = req_parameters.to_json
     end
   end
diff --git a/spec/openai/client/http_spec.rb b/spec/openai/client/http_spec.rb
index 471289f4..4c5814dc 100644
--- a/spec/openai/client/http_spec.rb
+++ b/spec/openai/client/http_spec.rb
@@ -1,4 +1,47 @@
 RSpec.describe OpenAI::HTTP do
+  describe "extra_headers" do
+    include WebMock::API
+
+    let(:client) { OpenAI::Client.new }
+    let(:custom_headers) { { "X-Custom-Header" => "custom-value", "X-Another" => "another-value" } }
+    let(:chat_url) { "https://api.openai.com/v1/chat/completions" }
+
+    before do
+      VCR.turn_off!
+      WebMock.disable_net_connect!
+      stub_request(:post, chat_url)
+        .to_return(status: 200, body: { choices: [] }.to_json, headers: {})
+    end
+
+    after do
+      WebMock.reset!
+      VCR.turn_on!
+    end
+
+    it "merges extra_headers into the request" do
+      client.chat(parameters: { model: "gpt-4", messages: [] }, extra_headers: custom_headers)
+
+      assert_requested(:post, chat_url, headers: custom_headers)
+    end
+
+    it "allows extra_headers to override default headers" do
+      client.chat(
+        parameters: { model: "gpt-4", messages: [] },
+        extra_headers: { "Content-Type" => "application/json; charset=utf-8" }
+      )
+
+      assert_requested(
+        :post, chat_url, headers: { "Content-Type" => "application/json; charset=utf-8" }
+      )
+    end
+
+    it "works without extra_headers (backward compatible)" do
+      client.chat(parameters: { model: "gpt-4", messages: [] })
+
+      assert_requested(:post, chat_url)
+    end
+  end
+
   describe "with an aggressive timeout" do
     let(:timeout_errors) { [Faraday::ConnectionFailed, Faraday::TimeoutError] }
     let(:timeout) { 0 }