The 32-year-old has signed a new two-year contract with the Hammers, who he joined in a £5million deal from Fulham in 2007.
Boa Morte’s previous deal was set to expire this summer.
He told the club’s official website: “I am delighted to sign the contract and can’t wait to get started.
“The new manager Avram Grant is going to play an attacking style and I hope to get involved in that.
“I am very happy to be at West Ham and look forward to scoring more goals and doing everything I can for the team.”
He continued: “To be honest, I did have more options and more offers from other people but I wanted to stay here.
“When the season finished, a few clubs came to me about signing for them but West Ham believed in me and things are looking positive here.
“We have a new manager and I have seen he has done good things with Chelsea and Portsmouth, reaching major finals twice. The fans also had an impact on my decision to stay and I look forward to playing for them again.”