diff --git a/packages/eslint-plugin/src/rules/no-inferrable-types.ts b/packages/eslint-plugin/src/rules/no-inferrable-types.ts
index 9adb4bca9ec..e77b694cc70 100644
--- a/packages/eslint-plugin/src/rules/no-inferrable-types.ts
+++ b/packages/eslint-plugin/src/rules/no-inferrable-types.ts
@@ -46,6 +46,8 @@ export default util.createRule<Options, MessageIds>({
     },
   ],
   create(context, [{ ignoreParameters, ignoreProperties }]) {
+    const sourceCode = context.getSourceCode();
+
     function isFunctionCall(
       init: TSESTree.Expression,
       callName: string,
@@ -215,7 +217,16 @@ export default util.createRule<Options, MessageIds>({
         data: {
           type,
         },
-        fix: fixer => fixer.remove(typeNode),
+        *fix(fixer) {
+          if (
+            (node.type === AST_NODE_TYPES.AssignmentPattern &&
+              node.left.optional) ||
+            (node.type === AST_NODE_TYPES.PropertyDefinition && node.definite)
+          ) {
+            yield fixer.remove(sourceCode.getTokenBefore(typeNode)!);
+          }
+          yield fixer.remove(typeNode);
+        },
       });
     }
 
diff --git a/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts b/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
index d85806b69c4..cfea578b9f6 100644
--- a/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
@@ -156,7 +156,54 @@ class Foo {
 
   invalid: [
     ...invalidTestCases,
-
+    {
+      // This is invalid TS semantic, but it's trivial to make valid anyway
+      code: 'const fn = (a?: number = 5) => {};',
+      output: 'const fn = (a = 5) => {};',
+      options: [
+        {
+          ignoreParameters: false,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'noInferrableType',
+          data: {
+            type: 'number',
+          },
+          line: 1,
+          column: 13,
+        },
+      ],
+    },
+    {
+      // This is invalid TS semantic, but it's trivial to make valid anyway
+      code: `
+class A {
+  a!: number = 1;
+}
+      `,
+      output: `
+class A {
+  a = 1;
+}
+      `,
+      options: [
+        {
+          ignoreProperties: false,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'noInferrableType',
+          data: {
+            type: 'number',
+          },
+          line: 3,
+          column: 3,
+        },
+      ],
+    },
     {
       code: "const fn = (a: number = 5, b: boolean = true, c: string = 'foo') => {};",
       output: "const fn = (a = 5, b = true, c = 'foo') => {};",