diff --git a/changelog.d/11595-windows-agent-ptrs-export.md b/changelog.d/11595-windows-agent-ptrs-export.md
new file mode 100644
index 0000000000..4b01ef6518
--- /dev/null
+++ b/changelog.d/11595-windows-agent-ptrs-export.md
@@ -0,0 +1 @@
+- **perry-runtime (Windows)**: `PERRY_AGENT_PTRS` is no longer `#[no_mangle]` on Windows. MSVC cannot export TLS across images, and the duplicate thread-local shim symbol broke every `x86_64-pc-windows-msvc` release build of perry-runtime since #11489.
diff --git a/crates/perry-runtime/src/agent_ptrs.rs b/crates/perry-runtime/src/agent_ptrs.rs
index 19d36f5173..d994e55873 100644
--- a/crates/perry-runtime/src/agent_ptrs.rs
+++ b/crates/perry-runtime/src/agent_ptrs.rs
@@ -37,7 +37,13 @@ pub struct AgentPtrs([Cell<*const u8>; AGENT_PTR_SLOTS]);
 /// `#[thread_local]` (not `thread_local!`) because generated code must be able
 /// to name the TLS symbol itself. Const-initialised and without drop glue, so
 /// no destructor is registered and a late read during teardown sees null.
-#[no_mangle]
+///
+/// Not exported on Windows: MSVC targets cannot export TLS across images, so
+/// rustc emits a thread-local shim for the static under the same symbol name
+/// and a `#[no_mangle]` static fails to build ("symbol `PERRY_AGENT_PTRS` is
+/// already defined"). Only ELF executables name it
+/// (`perry-codegen/src/expr/agent_ptr.rs`); Windows takes the accessor call.
+#[cfg_attr(not(windows), no_mangle)]
 #[thread_local]
 pub static PERRY_AGENT_PTRS: AgentPtrs =
     AgentPtrs([const { Cell::new(std::ptr::null()) }; AGENT_PTR_SLOTS]);