diff --git a/src/postgres_mcp/server.py b/src/postgres_mcp/server.py
index 90017d6..f3e2c8f 100644
--- a/src/postgres_mcp/server.py
+++ b/src/postgres_mcp/server.py
@@ -26,9 +26,9 @@
 from .index.llm_opt import LLMOptimizerTool
 from .index.presentation import TextPresentation
 from .moldes.model import AccessMode
-from .resource import register_resource_templates
 from .resource import format_error_response
 from .resource import format_text_response
+from .resource import register_resource_templates
 from .sql import SafeSqlDriver
 from .sql import check_hypopg_installation_status
 from .sql import obfuscate_password
diff --git a/src/postgres_mcp/utils/url.py b/src/postgres_mcp/utils/url.py
index 748fc73..925f62b 100644
--- a/src/postgres_mcp/utils/url.py
+++ b/src/postgres_mcp/utils/url.py
@@ -1,4 +1,5 @@
 from urllib.parse import quote
+from urllib.parse import unquote
 
 
 def fix_connection_url(url: str) -> str:
@@ -10,7 +11,9 @@ def fix_connection_url(url: str) -> str:
             user_pass = url[scheme_end:at_pos]
             if ":" in user_pass:
                 username, password = user_pass.split(":", 1)
-                encoded_password = quote(password, safe="")
+                # If password is already encoded, decode it.
+                plain_password = unquote(password)
+                encoded_password = quote(plain_password, safe="")
                 return url[:scheme_end] + username + ":" + encoded_password + url[at_pos:]
     except Exception as e:
         print(e)
diff --git a/tests/unit/utils/test_url.py b/tests/unit/utils/test_url.py
new file mode 100644
index 0000000..beb38b0
--- /dev/null
+++ b/tests/unit/utils/test_url.py
@@ -0,0 +1,23 @@
+import pytest
+
+from postgres_mcp.utils.url import fix_connection_url
+
+
+@pytest.mark.parametrize(
+    "input_url, expected_output",
+    [
+        ("postgresql://user:pass?word@localhost:5432/db", "postgresql://user:pass%3Fword@localhost:5432/db"),
+        ("postgresql://user:pass%3Fword@localhost:5432/db", "postgresql://user:pass%3Fword@localhost:5432/db"),
+        ("postgresql://user:pass%word@localhost:5432/db", "postgresql://user:pass%25word@localhost:5432/db"),
+        ("postgresql://user:?pass%25wo%%rd@localhost:5432/db", "postgresql://user:%3Fpass%25wo%25%25rd@localhost:5432/db"),
+    ],
+)
+def test_fix_connection_url_encoding(input_url: str, expected_output: str) -> None:
+    """Verifies that passwords are encoded once and only once."""
+    assert fix_connection_url(input_url) == expected_output
+
+
+def test_fix_connection_url_no_mutation():
+    """Ensure a standard safe URL is not changed."""
+    url = "postgresql://readonly:securepassword123@db.example.com:5432/postgres"
+    assert fix_connection_url(url) == url