New coach Giancarlo Italiano backed the 21-year-old, who played four games in the 2021-22 campaign but spent last season behind now-Perth Glory goalkeeper Oli Sail, to start ahead of veteran recruit Jack Duncan.
It paid off, with Paulsen making three crucial, goal-denying saves in difficult, hot conditions at CommBank Stadium in the first scoreless draw of the new season.
The Phoenix were largely kept on the back foot by Marko Rudan's Wanderers, who are aiming to build on reaching the finals last season.
Western Sydney dominated territory and chances but missed Milos Ninkovic's ability to unlock a defence, while Brandon Borrello played an hour off the back of international duties in England but went goalless.
Nicolas Milanovic was lively all game and forced an extraordinary leaping save from Paulsen in the seventh minute.
The young goalkeeper then brilliantly denied Marcus Antonsson in the 33rd, while the Wanderers forward headed over the bar eight minutes later.
Western Sydney counterpart Lawrence Thomas stood tall late in first-half added time when Kosta Barbarouses picked out Nicholas Pennington with a lovely ball, but the goalkeeper batted away the goal-bound header.
From the follow-up, Wellington striker Oskar Zawada nodded wide.
Paulsen picked up where he left off after the break.
The goalkeeper batted away a curling effort from Jack Clisby four minutes in.
Play was stopped in the 65th minute after a nasty clash of heads between Clisby and Wellington's Bozhidar Kraev, but both players were able to continue.
Clisby headed across the face of the goal in the 80th minute when he was picked out by Jorrit Hendrix, who dragged a shot of his own wide five minutes later.
Multiple players struggled with the heat and cramped up in the final 20 minutes.
17°C