diff --git a/lib/postgrex/utils.ex b/lib/postgrex/utils.ex
index 7923221a..73b067b6 100644
--- a/lib/postgrex/utils.ex
+++ b/lib/postgrex/utils.ex
@@ -84,16 +84,22 @@ defmodule Postgrex.Utils do
 
   @doc """
   Fills in the given `opts` with default options.
+  Only adds keys extracted via PGHOST if no endpoint-related keys are explicitly provided.
   """
   @spec default_opts(Keyword.t()) :: Keyword.t()
   def default_opts(opts) do
     {field, value} = extract_host(System.get_env("PGHOST"))
 
+    endpoint_keys = [:socket, :socket_dir, :hostname, :endpoints]
+    has_endpoint? = Enum.any?(endpoint_keys, &Keyword.has_key?(opts, &1))
+
     opts
     |> Keyword.put_new(:username, System.get_env("PGUSER") || System.get_env("USER"))
     |> Keyword.put_new(:password, System.get_env("PGPASSWORD"))
     |> Keyword.put_new(:database, System.get_env("PGDATABASE"))
-    |> Keyword.put_new(field, value)
+    |> then(fn opts ->
+      if has_endpoint?, do: opts, else: Keyword.put(opts, field, value)
+    end)
     |> Keyword.put_new(:port, System.get_env("PGPORT"))
     |> Keyword.update!(:port, &normalize_port/1)
     |> Keyword.put_new(:types, Postgrex.DefaultTypes)
diff --git a/test/utils/envs_test.exs b/test/utils/envs_test.exs
index bf6de333..7a3cb9a1 100644
--- a/test/utils/envs_test.exs
+++ b/test/utils/envs_test.exs
@@ -72,4 +72,37 @@ defmodule Utils.EnvsTest do
       assert ctx.opts[:socket] == <<0, "foo">>
     end
   end
+
+  describe "PGHOST with manual overrides" do
+    @env PGHOST: "/test/socket"
+    test "respects explicit hostname even if PGHOST is set" do
+      opts = Postgrex.Utils.default_opts(hostname: "localhost")
+
+      assert Keyword.get(opts, :hostname) == "localhost"
+      refute Keyword.has_key?(opts, :socket_dir)
+    end
+
+    @env PGHOST: "/test/socket"
+    test "respects explicit endpoints even if PGHOST is set" do
+      opts = Postgrex.Utils.default_opts(endpoints: [{"localhost", 5432}])
+
+      assert Keyword.get(opts, :endpoints) == [{"localhost", 5432}]
+      refute Keyword.has_key?(opts, :socket_dir)
+    end
+
+    @env PGHOST: "/test/socket"
+    test "respects explicit socket even if PGHOST is set" do
+      opts = Postgrex.Utils.default_opts(socket: "/var/run/postgresql")
+
+      assert Keyword.get(opts, :socket) == "/var/run/postgresql"
+      refute Keyword.has_key?(opts, :socket_dir)
+    end
+
+    @env PGHOST: "/test/socket"
+    test "respects explicit socket_dir even if PGHOST is set" do
+      opts = Postgrex.Utils.default_opts(socket_dir: "/another/test/socket")
+
+      assert Keyword.get(opts, :socket_dir) == "/another/test/socket"
+    end
+  end
 end