The Frenchman opened the scoring against the Seagulls by cutely flicking the ball home in a double nutmeg backheel - an emphatic way to mark his debut.
You can get behind JP to help him win Premier League Goal of the Month by voting for him here any time before 18:00 GMT on Monday, 8th March.
Mateta is up against Joao Moutinho, James Ward-Prowse, Bruno Fernandes, Mo Salah, Matt Lowton, Riyad Mahrez and Takumi Minamino for the award, so needs all the support he can get.
The winner will be announced at 13:00 GMT on Friday, 12th March. In the meantime, relive that night on the coast again below...