Petric, who was released by Fulham after his contract expired in July, links up with Sam Allardyce's side until the end of the season.
The Croatia international has been brought in by Allardyce after it was confirmed that striker Andy Carroll had suffered a foot injury.
"I'm very happy, excited and looking forward to training with the team and to the first game," the 32-year-old said.
"I know (the Premier League) and I'm happy to be back in the Premier League, because it's a fantastic league and I'm really looking forward to being part of this team and this club.
"I didn't speak to Sam (Allardyce) until today but I've heard a lot about him and I spoke to Guy Demel, who I know from my time at Hamburg and I'm sure I'll have a good time here.
"I remember playing at West Ham last year and it was a very tough game for us at Fulham. I think we lost 3-0. It's not easy to come here (as the away side) and take points away."
Petric joined Fulham from Hamburg on a one-year deal in July 2012, going on to score five goals in 23 appearances for Martin Jol's side.
‘I don’t think Liverpool would look at Ollie Watkins, a striker isn’t a pressing issue for them – it’s Arsenal who need one’ Former Reds star explains why his old club don’t need an out-and-out forward this summer
‘He’ll still be playing at 40 at a good level because he’s in such good shape and looks after himself so well. He does everything to be a top professional’: Ex-Liverpool coach insists Mohamed Salah has plenty more miles in the tank
