diff --git a/src/cli/operations/dev/__tests__/load-dev-env.test.ts b/src/cli/operations/dev/__tests__/load-dev-env.test.ts
new file mode 100644
index 000000000..a5e8d5b54
--- /dev/null
+++ b/src/cli/operations/dev/__tests__/load-dev-env.test.ts
@@ -0,0 +1,75 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+const { mockReadDeployedState, mockReadAWSDeploymentTargets, mockReadProjectSpec, mockFindConfigRoot, mockReadEnvFile } =
+  vi.hoisted(() => ({
+    mockReadDeployedState: vi.fn(),
+    mockReadAWSDeploymentTargets: vi.fn(),
+    mockReadProjectSpec: vi.fn(),
+    mockFindConfigRoot: vi.fn(),
+    mockReadEnvFile: vi.fn(),
+  }));
+
+const libMock = {
+  ConfigIO: class {
+    readDeployedState = mockReadDeployedState;
+    readAWSDeploymentTargets = mockReadAWSDeploymentTargets;
+    readProjectSpec = mockReadProjectSpec;
+  },
+  findConfigRoot: mockFindConfigRoot,
+  readEnvFile: mockReadEnvFile,
+};
+
+vi.mock('../../../../lib', () => libMock);
+vi.mock('../../../../lib/index.js', () => libMock);
+
+const { loadDevEnv } = await import('../load-dev-env.js');
+
+const deployedStateInUsWest2 = {
+  targets: { default: { resources: { memories: {} } } },
+};
+const usWest2Targets = [{ name: 'default', region: 'us-west-2' }];
+
+describe('loadDevEnv region injection (issue #1457)', () => {
+  beforeEach(() => {
+    mockFindConfigRoot.mockReturnValue('/project/agentcore');
+    mockReadEnvFile.mockResolvedValue({});
+    mockReadProjectSpec.mockResolvedValue({ agentCoreGateways: [] });
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    delete process.env.AWS_REGION;
+    delete process.env.AWS_DEFAULT_REGION;
+  });
+
+  it('injects the deployed target region even when the shell region differs', async () => {
+    process.env.AWS_REGION = 'us-east-1';
+    mockReadDeployedState.mockResolvedValue(deployedStateInUsWest2);
+    mockReadAWSDeploymentTargets.mockResolvedValue(usWest2Targets);
+
+    const { envVars } = await loadDevEnv('/project');
+
+    expect(envVars.AWS_REGION).toBe('us-west-2');
+    expect(envVars.AWS_DEFAULT_REGION).toBe('us-west-2');
+  });
+
+  it('lets an explicit AWS_REGION in the project .env override the target region', async () => {
+    mockReadDeployedState.mockResolvedValue(deployedStateInUsWest2);
+    mockReadAWSDeploymentTargets.mockResolvedValue(usWest2Targets);
+    mockReadEnvFile.mockResolvedValue({ AWS_REGION: 'eu-west-1' });
+
+    const { envVars } = await loadDevEnv('/project');
+
+    expect(envVars.AWS_REGION).toBe('eu-west-1');
+  });
+
+  it('omits region vars (and does not throw) when aws-targets is unreadable', async () => {
+    mockReadDeployedState.mockRejectedValue(new Error('no state'));
+    mockReadAWSDeploymentTargets.mockRejectedValue(new Error('no targets'));
+
+    const { envVars } = await loadDevEnv('/project');
+
+    expect(envVars.AWS_REGION).toBeUndefined();
+    expect(envVars.AWS_DEFAULT_REGION).toBeUndefined();
+  });
+});
diff --git a/src/cli/operations/dev/load-dev-env.ts b/src/cli/operations/dev/load-dev-env.ts
index d68204231..b2653f42f 100644
--- a/src/cli/operations/dev/load-dev-env.ts
+++ b/src/cli/operations/dev/load-dev-env.ts
@@ -3,6 +3,7 @@ import type { AgentEnvSpec } from '../../../schema';
 import { getGatewayEnvVars } from './gateway-env.js';
 import { getMemoryEnvVars } from './memory-env.js';
 import { getPaymentEnvVars } from './payment-env.js';
+import { getRegionEnvVars } from './region-env.js';
 
 export interface DevEnv {
   /** Merged env vars: deployed-state (gateway + memory + payment) first, then .env overrides */
@@ -21,12 +22,13 @@ export interface DevEnv {
 export async function loadDevEnv(workingDir: string, runtime?: AgentEnvSpec): Promise<DevEnv> {
   const configRoot = findConfigRoot(workingDir);
   const dotEnvVars = configRoot ? await readEnvFile(configRoot) : {};
+  const regionEnvVars = await getRegionEnvVars();
   const gatewayEnvVars = await getGatewayEnvVars();
   const memoryEnvVars = await getMemoryEnvVars();
   const paymentEnvVars = await getPaymentEnvVars(runtime);
 
   return {
-    envVars: { ...gatewayEnvVars, ...memoryEnvVars, ...paymentEnvVars, ...dotEnvVars },
+    envVars: { ...regionEnvVars, ...gatewayEnvVars, ...memoryEnvVars, ...paymentEnvVars, ...dotEnvVars },
     deployedMemoryCount: Object.keys(memoryEnvVars).length,
   };
 }
diff --git a/src/cli/operations/dev/region-env.ts b/src/cli/operations/dev/region-env.ts
new file mode 100644
index 000000000..685c9d301
--- /dev/null
+++ b/src/cli/operations/dev/region-env.ts
@@ -0,0 +1,31 @@
+import { ConfigIO } from '../../../lib/index.js';
+
+/**
+ * Resolve the deployed target's region as AWS_REGION / AWS_DEFAULT_REGION env
+ * vars for dev mode. Deployed resources (e.g. AgentCore Memory) live in the
+ * region recorded in aws-targets.json, but the local agent's AWS SDK falls back
+ * to the shell's AWS_REGION otherwise — so a shell region that is unset or
+ * differs from the deployed region makes calls like ListEvents hit the wrong
+ * region and fail with "Memory not found" (see issue #1457).
+ *
+ * Uses the same target the dev path already resolves: the first target in
+ * deployed state, matched against aws-targets.json by name.
+ */
+export async function getRegionEnvVars(): Promise<Record<string, string>> {
+  const configIO = new ConfigIO();
+
+  try {
+    const deployedState = await configIO.readDeployedState();
+    const targetName = Object.keys(deployedState?.targets ?? {})[0];
+    if (!targetName) return {};
+
+    const awsTargets = await configIO.readAWSDeploymentTargets();
+    const region = awsTargets.find(t => t.name === targetName)?.region;
+    if (!region) return {};
+
+    return { AWS_REGION: region, AWS_DEFAULT_REGION: region };
+  } catch {
+    // No deployed state or targets — leave region resolution to the SDK default chain
+    return {};
+  }
+}