diff --git a/.changeset/healthy-waves-cheat.md b/.changeset/healthy-waves-cheat.md
new file mode 100644
index 0000000000..c2c679974f
--- /dev/null
+++ b/.changeset/healthy-waves-cheat.md
@@ -0,0 +1,5 @@
+---
+'@hyperlane-xyz/sdk': patch
+---
+
+Add mailbox version const to SDK
diff --git a/typescript/sdk/src/consts/mailbox.ts b/typescript/sdk/src/consts/mailbox.ts
new file mode 100644
index 0000000000..b1e3d5be48
--- /dev/null
+++ b/typescript/sdk/src/consts/mailbox.ts
@@ -0,0 +1,2 @@
+// Pairs well with /utils/src/messages.ts#formatMessage
+export const MAILBOX_VERSION = 3;
diff --git a/typescript/sdk/src/index.ts b/typescript/sdk/src/index.ts
index 06195db0d0..f6616b3844 100644
--- a/typescript/sdk/src/index.ts
+++ b/typescript/sdk/src/index.ts
@@ -29,6 +29,7 @@ export {
   hyperlaneContractAddresses,
   hyperlaneEnvironments,
 } from './consts/environments';
+export { MAILBOX_VERSION } from './consts/mailbox';
 export { defaultMultisigConfigs } from './consts/multisigIsm';
 export { SEALEVEL_SPL_NOOP_ADDRESS } from './consts/sealevel';
 export {