diff --git a/dio/CHANGELOG.md b/dio/CHANGELOG.md
index f245beca8..b1db236df 100644
--- a/dio/CHANGELOG.md
+++ b/dio/CHANGELOG.md
@@ -5,6 +5,7 @@ See the [Migration Guide][] for the complete breaking changes list.**
 
 ## Unreleased
 
+- Fix url concatenation '/' handling
 - Remove `http` from `dev_dependencies`.
 
 ## 5.2.1+1
diff --git a/dio/lib/src/options.dart b/dio/lib/src/options.dart
index e43849216..756a66f37 100644
--- a/dio/lib/src/options.dart
+++ b/dio/lib/src/options.dart
@@ -1,3 +1,5 @@
+import 'dart:io';
+
 import 'package:meta/meta.dart';
 
 import 'adapter.dart';
@@ -585,20 +587,21 @@ class RequestOptions extends _RequestConfig with OptionsMixin {
 
   /// generate uri
   Uri get uri {
-    String url = path;
-    if (!url.startsWith(RegExp(r'https?:'))) {
-      url = baseUrl + url;
-      final s = url.split(':/');
-      if (s.length == 2) {
-        url = '${s[0]}:/${s[1].replaceAll('//', '/')}';
-      }
+    Uri uri = Uri.parse(path);
+
+    if (!uri.isAbsolute) {
+      uri = Uri.parse(baseUrl).resolveUri(uri);
     }
+
     final query = Transformer.urlEncodeQueryMap(queryParameters, listFormat);
     if (query.isNotEmpty) {
-      url += (url.contains('?') ? '&' : '?') + query;
+      final separator = uri.query.isNotEmpty ? '&' : '';
+      final mergedQuery = uri.query + separator + query;
+      uri = uri.replace(query: mergedQuery);
     }
+
     // Normalize the url.
-    return Uri.parse(url).normalizePath();
+    return uri.normalizePath();
   }
 
   /// Request data, can be any type.
diff --git a/dio/test/options_test.dart b/dio/test/options_test.dart
index 7f18566e6..5c85eadc5 100644
--- a/dio/test/options_test.dart
+++ b/dio/test/options_test.dart
@@ -469,4 +469,88 @@ void main() {
       expect(response.data, 'test');
     }
   });
+
+  test('Ensure consistent slash handling', () {
+    final dio = Dio();
+    final inputs = [
+      ['https://www.example.com', 'path'],
+      ['https://www.example.com/', 'path'],
+      ['https://www.example.com', '/path'],
+      ['https://www.example.com/', '/path'],
+    ];
+
+    for (final input in inputs) {
+      final baseUrl = input[0];
+      final path = input[1];
+      dio.options.baseUrl = baseUrl;
+      final actual = Options().compose(dio.options, path).uri.toString();
+      expect(actual, equals('https://www.example.com/path'));
+    }
+  });
+
+  test('Should return absolute URI when path is already absolute', () {
+    final baseUrl = 'https://www.example.com';
+    final path = 'https://www.another-example.com/path/to/resource';
+    final baseOptions = BaseOptions(baseUrl: baseUrl);
+
+    final actual = Options().compose(baseOptions, path).uri;
+
+    expect(actual.toString(), equals(path));
+  });
+
+  test('Should resolve relative path with base URL', () {
+    final baseUrl = 'https://www.example.com';
+    final path = '/path/to/resource';
+    final baseOptions = BaseOptions(baseUrl: baseUrl);
+
+    final actual = Options().compose(baseOptions, path).uri;
+
+    expect(
+      actual.toString(),
+      equals('https://www.example.com/path/to/resource'),
+    );
+  });
+
+  test('Should add query parameters to the URI', () {
+    final baseUrl = 'https://www.example.com';
+    final path = '/path/to/resource';
+    final baseOptions = BaseOptions(
+      baseUrl: baseUrl,
+      queryParameters: {'param1': 'value1'},
+    );
+
+    final actual = Options().compose(
+      baseOptions,
+      path,
+      queryParameters: {'param2': 'value2'},
+    ).uri;
+
+    expect(
+      actual.queryParameters,
+      equals({
+        'param1': 'value1',
+        'param2': 'value2',
+      }),
+    );
+  });
+
+  test('Should preserve path query parameters to the URI', () {
+    final baseUrl = 'https://www.example.com';
+    final path = '/path/to/resource?param1=value1';
+    final baseOptions = BaseOptions(baseUrl: baseUrl);
+
+    final actual = Options(listFormat: ListFormat.csv).compose(
+      baseOptions,
+      path,
+      queryParameters: {'param2': 'value2'},
+    ).uri;
+
+    expect(
+      actual.queryParameters,
+      equals({
+        'param1': 'value1',
+        'param2': 'value2',
+      }),
+    );
+  });
 }