diff --git a/packages/core/src/utils/environmentContext.test.ts b/packages/core/src/utils/environmentContext.test.ts
index a43bb5fd56..42b2316955 100644
--- a/packages/core/src/utils/environmentContext.test.ts
+++ b/packages/core/src/utils/environmentContext.test.ts
@@ -165,6 +165,29 @@ describe('getEnvironmentContext', () => {
     expect(getFolderStructure).not.toHaveBeenCalled();
   });
 
+  it('should exclude environment memory when JIT context is enabled', async () => {
+    (mockConfig as Record<string, unknown>)['isJitContextEnabled'] = vi
+      .fn()
+      .mockReturnValue(true);
+
+    const parts = await getEnvironmentContext(mockConfig as Config);
+
+    const context = parts[0].text;
+    expect(context).not.toContain('Mock Environment Memory');
+    expect(mockConfig.getEnvironmentMemory).not.toHaveBeenCalled();
+  });
+
+  it('should include environment memory when JIT context is disabled', async () => {
+    (mockConfig as Record<string, unknown>)['isJitContextEnabled'] = vi
+      .fn()
+      .mockReturnValue(false);
+
+    const parts = await getEnvironmentContext(mockConfig as Config);
+
+    const context = parts[0].text;
+    expect(context).toContain('Mock Environment Memory');
+  });
+
   it('should handle read_many_files returning no content', async () => {
     const mockReadManyFilesTool = {
       build: vi.fn().mockReturnValue({
diff --git a/packages/core/src/utils/environmentContext.ts b/packages/core/src/utils/environmentContext.ts
index 88dd1aab68..d5bdd2d75b 100644
--- a/packages/core/src/utils/environmentContext.ts
+++ b/packages/core/src/utils/environmentContext.ts
@@ -57,7 +57,12 @@ export async function getEnvironmentContext(config: Config): Promise<Part[]> {
     ? await getDirectoryContextString(config)
     : '';
   const tempDir = config.storage.getProjectTempDir();
-  const environmentMemory = config.getEnvironmentMemory();
+  // When JIT context is enabled, project memory is already included in the
+  // system instruction via renderUserMemory(). Skip it here to avoid sending
+  // the same GEMINI.md content twice.
+  const environmentMemory = config.isJitContextEnabled?.()
+    ? ''
+    : config.getEnvironmentMemory();
 
   const context = `
 <session_context>