diff --git a/csharp/src/Hive2/HiveServer2Connection.cs b/csharp/src/Hive2/HiveServer2Connection.cs
index e2f503c..1fc3d28 100644
--- a/csharp/src/Hive2/HiveServer2Connection.cs
+++ b/csharp/src/Hive2/HiveServer2Connection.cs
@@ -841,7 +841,7 @@ protected internal string GetProductVersion()
             return fileVersionInfo.ProductVersion ?? GetProductVersionDefault();
         }
 
-        protected static Uri GetBaseAddress(string? uri, string? hostName, string? path, string? port, string hostOptionName, bool isTlsEnabled)
+        protected internal static Uri GetBaseAddress(string? uri, string? hostName, string? path, string? port, string hostOptionName, bool isTlsEnabled)
         {
             // Uri property takes precedent.
             if (!string.IsNullOrWhiteSpace(uri))
@@ -874,7 +874,16 @@ protected static Uri GetBaseAddress(string? uri, string? hostName, string? path,
             else
                 throw new ArgumentOutOfRangeException(nameof(port), portNumber, $"Port number is not in a valid range.");
 
-            Uri baseAddress = new UriBuilder(uriScheme, hostName, uriPort, path).Uri;
+            // UriBuilder percent-encodes '?' as '%3F' when a query string is embedded
+            // in the path argument (e.g. /sql/1.0/warehouses/<id>?o=<orgId>).
+            // Use the overload that takes extraValue so the query is passed correctly.
+            int queryIndex = path?.IndexOf('?') ?? -1;
+            Uri baseAddress = new UriBuilder(
+                uriScheme,
+                hostName,
+                uriPort,
+                queryIndex >= 0 ? path!.Substring(0, queryIndex) : path,
+                queryIndex >= 0 ? path!.Substring(queryIndex) : string.Empty).Uri;
             return baseAddress;
         }
 
diff --git a/csharp/test/Hive2/HiveServer2ConnectionGetBaseAddressTest.cs b/csharp/test/Hive2/HiveServer2ConnectionGetBaseAddressTest.cs
new file mode 100644
index 0000000..29eb8c2
--- /dev/null
+++ b/csharp/test/Hive2/HiveServer2ConnectionGetBaseAddressTest.cs
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2025 ADBC Drivers Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+using System;
+using AdbcDrivers.HiveServer2.Hive2;
+using AdbcDrivers.HiveServer2.Spark;
+using Xunit;
+
+namespace AdbcDrivers.Tests.HiveServer2.Hive2
+{
+    /// <summary>
+    /// Unit tests for HiveServer2Connection.GetBaseAddress, focusing on correct
+    /// handling of HTTP paths that contain query parameters (e.g. ?o=orgId).
+    /// </summary>
+    public class HiveServer2ConnectionGetBaseAddressTest
+    {
+        /// <summary>
+        /// Verifies that a path containing a query parameter (e.g. Databricks warehouse
+        /// paths with ?o=orgId) is not percent-encoded. The '?' must remain a literal
+        /// query separator and not become %3F in the resulting URI.
+        /// </summary>
+        [Fact]
+        public void GetBaseAddress_PathWithQueryParam_DoesNotPercentEncodeQuestionMark()
+        {
+            Uri result = InvokeGetBaseAddress(
+                uri: null,
+                hostName: "test.server.com",
+                path: "/sql/1.0/warehouses/abc123?o=999888777",
+                port: "443",
+                isTlsEnabled: true);
+
+            Assert.DoesNotContain("%3F", result.ToString());
+            Assert.Equal("/sql/1.0/warehouses/abc123", result.AbsolutePath);
+            Assert.Equal("o=999888777", result.Query.TrimStart('?'));
+            Assert.Equal("https://test.server.com/sql/1.0/warehouses/abc123?o=999888777", result.ToString());
+        }
+
+        /// <summary>
+        /// Verifies that a plain path without a query parameter is unchanged.
+        /// </summary>
+        [Fact]
+        public void GetBaseAddress_PathWithoutQueryParam_ReturnsExpectedUri()
+        {
+            Uri result = InvokeGetBaseAddress(
+                uri: null,
+                hostName: "test.server.com",
+                path: "/sql/1.0/warehouses/abc123",
+                port: "443",
+                isTlsEnabled: true);
+
+            Assert.Equal("/sql/1.0/warehouses/abc123", result.AbsolutePath);
+            Assert.Equal(string.Empty, result.Query);
+            Assert.Equal("https://test.server.com/sql/1.0/warehouses/abc123", result.ToString());
+        }
+
+        /// <summary>
+        /// Verifies that when a full URI is provided it is returned as-is, bypassing
+        /// the UriBuilder path entirely.
+        /// </summary>
+        [Fact]
+        public void GetBaseAddress_FullUri_ReturnsUriDirectly()
+        {
+            string fullUri = "https://test.server.com/sql/1.0/warehouses/abc123";
+
+            Uri result = InvokeGetBaseAddress(
+                uri: fullUri,
+                hostName: null,
+                path: null,
+                port: null,
+                isTlsEnabled: true);
+
+            Assert.Equal(new Uri(fullUri), result);
+        }
+
+        private static Uri InvokeGetBaseAddress(string? uri, string? hostName, string? path, string? port, bool isTlsEnabled)
+        {
+            return HiveServer2Connection.GetBaseAddress(uri, hostName, path, port, SparkParameters.HostName, isTlsEnabled);
+        }
+    }
+}