diff --git a/packages/sdk/src/types/json.ts b/packages/sdk/src/types/json.ts
index fe1d479e6..74757a3c1 100644
--- a/packages/sdk/src/types/json.ts
+++ b/packages/sdk/src/types/json.ts
@@ -228,8 +228,11 @@ export function jsonStringify(
  * This should be used if you want to manually deserialize the inner property values, as the serialization is irreversible.
  *
  * @param value A JavaScript value, usually an object or array, to be converted.
- * @param bigintFormat Determines how to handle bigints.
- * Can be set to either 'number' (uses 'json-bigint to safely serialize), 'string', or undefined (must be taken care of in replacer function)
+ * @param bigintFormat Determines how to handle bigints. Can be set to either:
+ * - `'number'`: uses 'json-bigint to safely serialize,
+ * - `'string'`: converts `bigint` to strings
+ * - `undefined`: must be taken care of manually, e.g. in replacer function.
+ * Defaults to 'number'
  * @param replacer A function that transforms the results.
  * @param space Adds indentation, white space, and line break characters to the return-value JSON text to make it easier to read.
  */
@@ -239,21 +242,30 @@ export function jsonUnwrapStringify(
     replacer?: ReplacerFun,
     space?: string | number
 ): string {
-    function replacerFunction(this: any, key: string, value: any) {
-        let transformedValue = ccdUnwrapReplacer.call(this, key, value);
-
+    function replaceBigintValue(value: any): any {
         switch (bigintFormat) {
             case 'string':
                 if (typeof value === 'bigint') {
-                    transformedValue = value.toString();
+                    return value.toString();
                 }
             default:
-                break;
+                return value;
         }
+    }
+
+    function replacerFunction(this: any, key: string, value: any) {
+        let transformedValue = ccdUnwrapReplacer.call(this, key, value);
+        transformedValue = replaceBigintValue(transformedValue);
         return replacer?.call(this, key, transformedValue) ?? transformedValue;
     }
 
+    let replaced = input;
+
+    if (typeof input !== 'object') {
+        replaced = replaceBigintValue(replaced);
+    }
+
     const stringify =
         bigintFormat === 'number' ? JSONBig.stringify : JSON.stringify;
-    return stringify(input, replacerFunction, space);
+    return stringify(replaced, replacerFunction, space);
 }
diff --git a/packages/sdk/test/ci/types/json.test.ts b/packages/sdk/test/ci/types/json.test.ts
index 706aca9d3..758d8737f 100644
--- a/packages/sdk/test/ci/types/json.test.ts
+++ b/packages/sdk/test/ci/types/json.test.ts
@@ -87,6 +87,43 @@ describe('jsonStringify', () => {
     });
 });
 
+describe(jsonUnwrapStringify, () => {
+    test('Serializes bigint values as expected', () => {
+        const t = 100n;
+        expect(jsonUnwrapStringify(t)).toEqual('100');
+        expect(jsonUnwrapStringify(t, 'string')).toEqual('"100"');
+        expect(
+            jsonUnwrapStringify(t, undefined, (_, v) =>
+                typeof v === 'bigint' ? -v : v
+            )
+        ).toEqual('-100');
+    });
+
+    test('Serializes nested bigint (arrays) values as expected', () => {
+        const t = [100n, 200n];
+        expect(jsonUnwrapStringify(t)).toEqual('[100,200]');
+        expect(jsonUnwrapStringify(t, 'string')).toEqual('["100","200"]');
+        expect(
+            jsonUnwrapStringify(t, undefined, (_, v) =>
+                typeof v === 'bigint' ? -v : v
+            )
+        ).toEqual('[-100,-200]');
+    });
+
+    test('Serializes nested bigint (objects) values as expected', () => {
+        const t = { a: 100n, b: 200n };
+        expect(jsonUnwrapStringify(t)).toEqual('{"a":100,"b":200}');
+        expect(jsonUnwrapStringify(t, 'string')).toEqual(
+            '{"a":"100","b":"200"}'
+        );
+        expect(
+            jsonUnwrapStringify(t, undefined, (_, v) =>
+                typeof v === 'bigint' ? -v : v
+            )
+        ).toEqual('{"a":-100,"b":-200}');
+    });
+});
+
 describe('ContractName', () => {
     test('Unwraps as expected', () => {
         const t = ContractName.fromString('some-name');
@@ -151,6 +188,12 @@ describe('SequenceNumber', () => {
         let t = SequenceNumber.create(300);
         let e = '300';
         expect(jsonUnwrapStringify(t)).toEqual(e);
+        expect(jsonUnwrapStringify(t, 'string')).toEqual(`"${e}"`);
+        expect(
+            jsonUnwrapStringify(t, undefined, (_, v) =>
+                typeof v === 'bigint' ? -v : v
+            )
+        ).toEqual('-300');
 
         // Test for numbers bigger than Number.MAX_SAFE_INTEGER
         t = SequenceNumber.create(9007199254740997n);
@@ -204,6 +247,9 @@ describe('ContractAddress', () => {
         let t = ContractAddress.create(100, 10);
         let e = '{"index":100,"subindex":10}';
         expect(jsonUnwrapStringify(t)).toEqual(e);
+        expect(jsonUnwrapStringify(t, 'string')).toEqual(
+            '{"index":"100","subindex":"10"}'
+        );
 
         // Test for numbers bigger than Number.MAX_SAFE_INTEGER
         t = ContractAddress.create(9007199254740997n, 10);