On the club's official website Perez expressed his happiness on the completion of the move, saying: “I’m very happy to be here at such a historic club. I’m very excited, as West Ham are giving me the chance to stay in the Premier League and I’m very happy to be part of this new project.
“West Ham have great fans and play in an amazing stadium, so to sign here brings me great joy. I’m very motivated.”
The acquisition of the number nine is Manuel Pellegrini's ninth signing since his arrival this summer. Perez joins the high profile additions of Felipe Anderson, Issa Diop, Andriy Yarmolenko as well as former teammate Jack Wilshere.
The first images of the new signing were seen in Wilshere's Instagram story, where he snapped a shot of Perez in the Hammer's training kit with a huge smile on his face.
This move represents a good chance for the striker to get his Premier League career back on track. His miserable two years at Arsenal are now firmly behind him, so when given the chance he needs to make an impact. Under Pellegrini he has a fantastic boss whose style of football earned him three pieces of silverware during his time at Manchester City.
Perez will add some more competition to the strikers already on the Hammers books - Marko Arnautovic, Javier Hernandez and Michail Antonio, who alongside the injured Andy Carroll will now have to work even harder to nail down their spots this season.
Perez joined Arsenal from Deportivo La Coruna in a reported £17.1m deal in August 2016 but failed to impress former boss Arsene Wenger, making only a handful of appearances during his two-year stint at the club.
Following the arrivals of Alexandre Lacazette and Pierre-Emerick Aubameyang, the 29-year-old spent the entirety of last season on loan to his former side Deportivo La Coruna where he managed eight goals and six assists from 37 appearances.
His form clearly improved back at his former club as he showed flashes of what earned him the move to the Premier League in the first place. For one reason or another it just wouldn't work out for Perez at Arsenal, with Unai Emery deeming him surplus to the club's requirements.
This season he will show if he can make it in the top tier of English football or whether he will continue to struggle, but if he is able to repeat his form from Deportivo at West Ham, he could be seen as a steal for only £5m.