The 26-year-old left the Gunners after his contract expired, leaving him with a number of potential clubs interested in getting his signature.
Speaking to the Independent, Wilshere stated that his decision to move to the London Stadium was driven by his desire to play at his boyhood club.
"I've had a bond with West Ham since growing up as a kid, going to Upton Park, looking up to the players.
"Obviously I had to consider all my options - abroad and in England - but once I sat down, it was clear for me. They've got real ambitions, they're playing in a big stadium in front of good fans, and we can build something special.
"As a team, they went through quite a lot last year, but they're really tight. That's going to help us going forward."
The player also revealed who he looked up to the most when he was a child, in the days when he used to go to Upton Park.
"Paolo Di Canio was my all-time hero. That team with Trevor Sinclair, even as far back as Julian Dicks.
"Then when I got a little bit older, I really looked up to Joe Cole. I remember watching him in the Youth Cup as a kid. We beat Coventry about 9-0 [in 1999], and he was unbelievable. As a young player, I wanted to be like him."