diff --git a/browser/net/BUILD.gn b/browser/net/BUILD.gn
index 2984b6a3d5a..096cdde7bcb 100644
--- a/browser/net/BUILD.gn
+++ b/browser/net/BUILD.gn
@@ -50,6 +50,7 @@ source_set("browser_tests") {
     "//components/content_settings/core/browser:cookie_settings",
     "//components/prefs",
     "//services/network/public/cpp",
+    "//testing/gmock",
   ]
   if (!is_android) {
     deps += [ "//chrome/test:test_support_ui" ]
diff --git a/browser/net/brave_service_key_network_delegate_helper.cc b/browser/net/brave_service_key_network_delegate_helper.cc
index 3ee79dd6843..c7f5c938d20 100644
--- a/browser/net/brave_service_key_network_delegate_helper.cc
+++ b/browser/net/brave_service_key_network_delegate_helper.cc
@@ -6,10 +6,14 @@
 #include "brave/browser/net/brave_service_key_network_delegate_helper.h"
 
 #include <string>
+#include <string_view>
 #include <vector>
 
+#include "base/containers/fixed_flat_set.h"
 #include "base/no_destructor.h"
 #include "brave/components/brave_rewards/core/buildflags/buildflags.h"
+#include "brave/components/brave_search/common/buildflags/buildflags.h"
+#include "brave/components/brave_service_keys/brave_service_key_utils.h"
 #include "brave/components/constants/brave_services_key.h"
 #include "brave/components/constants/network_constants.h"
 #include "brave/components/update_client/buildflags.h"
@@ -23,6 +27,13 @@
 
 namespace brave {
 
+namespace {
+
+constexpr auto kSearchDomains = base::MakeFixedFlatSet<std::string_view>(
+    {"search.brave.com", "search.brave.software"});
+
+}  // namespace
+
 template <template <typename> class T>
 int OnBeforeStartTransaction_BraveServiceKey(
     net::HttpRequestHeaders* headers,
@@ -43,12 +54,20 @@ int OnBeforeStartTransaction_BraveServiceKey(
   const GURL& url = ctx->request_url();
 
   if (url.SchemeIs(url::kHttpsScheme)) {
-    if (std::any_of(
+    const bool is_search_domain = kSearchDomains.contains(url.host());
+    if (is_search_domain ||
+        std::any_of(
             allowed_domains->begin(), allowed_domains->end(),
             [&url](const auto& domain) { return url.DomainIs(domain); })) {
       headers->SetHeader(kBraveServicesKeyHeader,
                          BUILDFLAG(BRAVE_SERVICES_KEY));
     }
+    if (is_search_domain) {
+      const auto authorization = brave_service_keys::GetAuthorizationHeader(
+          BUILDFLAG(SERVICE_KEY_SEARCH), /*headers=*/{}, url, ctx->method(),
+          {"(request-target)"});
+      headers->SetHeader(authorization.first, authorization.second);
+    }
   }
   return net::OK;
 }
diff --git a/browser/net/brave_service_key_network_delegate_helper_browsertest.cc b/browser/net/brave_service_key_network_delegate_helper_browsertest.cc
index bb4fd358555..a55555888b4 100644
--- a/browser/net/brave_service_key_network_delegate_helper_browsertest.cc
+++ b/browser/net/brave_service_key_network_delegate_helper_browsertest.cc
@@ -3,6 +3,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+#include <string>
+
+#include "base/containers/map_util.h"
 #include "brave/components/constants/network_constants.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/test/base/in_process_browser_test.h"
@@ -13,6 +16,7 @@
 #include "content/public/test/test_utils.h"
 #include "net/dns/mock_host_resolver.h"
 #include "net/test/embedded_test_server/http_request.h"
+#include "testing/gmock/include/gmock/gmock.h"
 
 class BraveServiceKeyNetworkDelegateBrowserTest : public InProcessBrowserTest {
  public:
@@ -35,6 +39,9 @@ class BraveServiceKeyNetworkDelegateBrowserTest : public InProcessBrowserTest {
     base::AutoLock auto_lock(header_result_lock_);
 
     header_result_ = request.headers.contains("BraveServiceKey");
+    const std::string* auth =
+        base::FindOrNull(request.headers, "Authorization");
+    authorization_header_ = auth ? *auth : std::string();
   }
 
   void SetUpCommandLine(base::CommandLine* command_line) override {
@@ -59,11 +66,17 @@ class BraveServiceKeyNetworkDelegateBrowserTest : public InProcessBrowserTest {
     return header_result_;
   }
 
+  std::string authorization_header() {
+    base::AutoLock auto_lock(header_result_lock_);
+    return authorization_header_;
+  }
+
  private:
   content::ContentMockCertVerifier mock_cert_verifier_;
   net::test_server::EmbeddedTestServer https_server_;
   mutable base::Lock header_result_lock_;
   bool header_result_ = false;
+  std::string authorization_header_;
 };
 
 IN_PROC_BROWSER_TEST_F(BraveServiceKeyNetworkDelegateBrowserTest,
@@ -98,4 +111,37 @@ IN_PROC_BROWSER_TEST_F(BraveServiceKeyNetworkDelegateBrowserTest,
   GURL target = https_server().GetURL(kExtensionUpdaterDomain, "/index.html");
   ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
   EXPECT_TRUE(header_result());
+
+  target = https_server().GetURL("search.brave.com", "/index.html");
+  ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
+  EXPECT_TRUE(header_result());
+
+  target = https_server().GetURL("search.brave.software", "/index.html");
+  ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
+  EXPECT_TRUE(header_result());
+}
+
+IN_PROC_BROWSER_TEST_F(BraveServiceKeyNetworkDelegateBrowserTest,
+                       IncludesAuthorizationHeaderForSearchDomains) {
+  GURL target = https_server().GetURL("search.brave.com", "/index.html");
+  ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
+  EXPECT_THAT(authorization_header(),
+              ::testing::StartsWith("Signature keyId="));
+  EXPECT_THAT(authorization_header(),
+              ::testing::HasSubstr("headers=\"(request-target)\""));
+
+  target = https_server().GetURL("search.brave.software", "/index.html");
+  ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
+  EXPECT_THAT(authorization_header(),
+              ::testing::StartsWith("Signature keyId="));
+  EXPECT_THAT(authorization_header(),
+              ::testing::HasSubstr("headers=\"(request-target)\""));
+
+  target = https_server().GetURL(kExtensionUpdaterDomain, "/index.html");
+  ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
+  EXPECT_TRUE(authorization_header().empty());
+
+  target = https_server().GetURL("brave.com", "/index.html");
+  ASSERT_TRUE(ui_test_utils::NavigateToURL(browser(), target));
+  EXPECT_TRUE(authorization_header().empty());
 }
diff --git a/browser/net/sources.gni b/browser/net/sources.gni
index c56829197e9..60966734878 100644
--- a/browser/net/sources.gni
+++ b/browser/net/sources.gni
@@ -68,6 +68,7 @@ brave_browser_net_deps = [
   "//brave/components/brave_rewards/core",
   "//brave/components/brave_rewards/core/buildflags",
   "//brave/components/brave_search/common",
+  "//brave/components/brave_search/common/buildflags",
   "//brave/components/brave_service_keys",
   "//brave/components/brave_shields/content/browser",
   "//brave/components/brave_shields/core/browser",
diff --git a/build/commands/lib/buildArgs.ts b/build/commands/lib/buildArgs.ts
index 604c4f3b620..ab0612d9a89 100644
--- a/build/commands/lib/buildArgs.ts
+++ b/build/commands/lib/buildArgs.ts
@@ -37,6 +37,7 @@ const FORWARD_ENV_CONFIG_VARS_TO_GN_ARGS = [
   'rewards_grant_staging_endpoint',
   'safebrowsing_api_endpoint',
   'service_key_aichat',
+  'service_key_search',
   'service_key_stt',
   'sparkle_dsa_private_key_file',
   'sparkle_eddsa_private_key',
diff --git a/components/brave_search/common/buildflags/BUILD.gn b/components/brave_search/common/buildflags/BUILD.gn
new file mode 100644
index 00000000000..258dc6d5587
--- /dev/null
+++ b/components/brave_search/common/buildflags/BUILD.gn
@@ -0,0 +1,19 @@
+# Copyright (c) 2026 The Brave Authors. All rights reserved.
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import("//build/buildflag_header.gni")
+
+declare_args() {
+  service_key_search = ""
+}
+
+if (is_official_build) {
+  assert(service_key_search != "")
+}
+
+buildflag_header("buildflags") {
+  header = "buildflags.h"
+  flags = [ "SERVICE_KEY_SEARCH=\"$service_key_search\"" ]
+}