diff --git a/tools/workspace/fcl_internal/patches/cassert.patch b/tools/workspace/fcl_internal/patches/cassert.patch
new file mode 100644
index 000000000000..56a9745f9d29
--- /dev/null
+++ b/tools/workspace/fcl_internal/patches/cassert.patch
@@ -0,0 +1,12 @@
+Add missing #include statement
+
+--- include/fcl/common/types.h
++++ include/fcl/common/types.h
+@@ -38,6 +38,7 @@
+ #ifndef FCL_DATA_TYPES_H
+ #define FCL_DATA_TYPES_H
+ 
++#include <cassert>
+ #include <cstddef>
+ #include <cstdint>
+ #include <vector>
diff --git a/tools/workspace/fcl_internal/repository.bzl b/tools/workspace/fcl_internal/repository.bzl
index 642f7de8aeeb..06c32300ba90 100644
--- a/tools/workspace/fcl_internal/repository.bzl
+++ b/tools/workspace/fcl_internal/repository.bzl
@@ -11,5 +11,8 @@ def fcl_internal_repository(
         commit = "df2702ca5e703dec98ebd725782ce13862e87fc8",
         sha256 = "3ebcf2470a3ee372440cdec4cb78d1723411c3cf84f419679c2c85317c4c2dae",  # noqa
         build_file = ":package.BUILD.bazel",
+        patches = [
+            ":patches/cassert.patch",
+        ],
         mirrors = mirrors,
     )