diff --git a/crates/oxc_ast/src/ast/ts.rs b/crates/oxc_ast/src/ast/ts.rs
index 8a12cbb11ec72..d5e922c307c07 100644
--- a/crates/oxc_ast/src/ast/ts.rs
+++ b/crates/oxc_ast/src/ast/ts.rs
@@ -782,7 +782,11 @@ pub enum TSTypePredicateName<'a> {
     This(TSThisType),
 }
 
-#[visited_node(scope(ScopeFlags::TsModuleBlock), enter_scope_before(body))]
+#[visited_node(
+    scope(ScopeFlags::TsModuleBlock),
+    enter_scope_before(body),
+    strict_if(self.body.as_ref().is_some_and(|body| body.is_strict()))
+)]
 #[derive(Debug)]
 #[cfg_attr(feature = "serialize", derive(Serialize, Tsify))]
 #[cfg_attr(feature = "serialize", serde(tag = "type", rename_all = "camelCase"))]
diff --git a/crates/oxc_ast/src/ast_impl/ts.rs b/crates/oxc_ast/src/ast_impl/ts.rs
index f28bf1750a7e6..749ab3325d654 100644
--- a/crates/oxc_ast/src/ast_impl/ts.rs
+++ b/crates/oxc_ast/src/ast_impl/ts.rs
@@ -153,6 +153,10 @@ impl<'a> TSModuleDeclaration<'a> {
     ) -> Self {
         Self { span, id, body, kind, declare, scope_id: Cell::default() }
     }
+
+    pub fn is_strict(&self) -> bool {
+        self.body.as_ref().is_some_and(TSModuleDeclarationBody::is_strict)
+    }
 }
 
 impl<'a> Hash for TSModuleDeclaration<'a> {
@@ -177,6 +181,18 @@ impl<'a> TSModuleDeclarationName<'a> {
     }
 }
 
+impl<'a> TSModuleDeclarationBody<'a> {
+    pub fn is_strict(&self) -> bool {
+        matches!(self, Self::TSModuleBlock(block) if block.is_strict())
+    }
+}
+
+impl<'a> TSModuleBlock<'a> {
+    pub fn is_strict(&self) -> bool {
+        self.directives.iter().any(Directive::is_use_strict)
+    }
+}
+
 impl<'a> Decorator<'a> {
     /// Get the name of the decorator
     /// ```ts
diff --git a/crates/oxc_ast/src/visit/visit.rs b/crates/oxc_ast/src/visit/visit.rs
index 72d9741957a34..022a7a887000e 100644
--- a/crates/oxc_ast/src/visit/visit.rs
+++ b/crates/oxc_ast/src/visit/visit.rs
@@ -2647,7 +2647,13 @@ pub mod walk {
             TSModuleDeclarationName::Identifier(ident) => visitor.visit_identifier_name(ident),
             TSModuleDeclarationName::StringLiteral(lit) => visitor.visit_string_literal(lit),
         }
-        visitor.enter_scope(ScopeFlags::TsModuleBlock);
+        visitor.enter_scope({
+            let mut flags = ScopeFlags::TsModuleBlock;
+            if decl.is_strict() {
+                flags |= ScopeFlags::StrictMode;
+            }
+            flags
+        });
         match &decl.body {
             Some(TSModuleDeclarationBody::TSModuleDeclaration(decl)) => {
                 visitor.visit_ts_module_declaration(decl);
diff --git a/crates/oxc_ast/src/visit/visit_mut.rs b/crates/oxc_ast/src/visit/visit_mut.rs
index 20df92f975ee7..e39c0aa5e6b3c 100644
--- a/crates/oxc_ast/src/visit/visit_mut.rs
+++ b/crates/oxc_ast/src/visit/visit_mut.rs
@@ -2727,7 +2727,13 @@ pub mod walk_mut {
             TSModuleDeclarationName::Identifier(ident) => visitor.visit_identifier_name(ident),
             TSModuleDeclarationName::StringLiteral(lit) => visitor.visit_string_literal(lit),
         }
-        visitor.enter_scope(ScopeFlags::TsModuleBlock);
+        visitor.enter_scope({
+            let mut flags = ScopeFlags::TsModuleBlock;
+            if decl.is_strict() {
+                flags |= ScopeFlags::StrictMode;
+            }
+            flags
+        });
         match &mut decl.body {
             Some(TSModuleDeclarationBody::TSModuleDeclaration(decl)) => {
                 visitor.visit_ts_module_declaration(decl);
diff --git a/crates/oxc_semantic/src/builder.rs b/crates/oxc_semantic/src/builder.rs
index 9aa732819b867..267274d14a713 100644
--- a/crates/oxc_semantic/src/builder.rs
+++ b/crates/oxc_semantic/src/builder.rs
@@ -424,7 +424,7 @@ impl<'a> Visit<'a> for SemanticBuilder<'a> {
             let parent_scope_flags = self.scope.get_flags(parent_scope_id);
 
             if !strict_mode
-                && parent_scope_flags.is_function()
+                && (parent_scope_flags.is_function() || parent_scope_flags.is_ts_module_block())
                 && parent_scope_flags.is_strict_mode()
             {
                 strict_mode = true;