The centre-back's deal at Upton Park had been due to expire at the end of next season.
But he has now put pen to paper on an agreement that will see him remain in east London for the next five years.
And Tomkins is excited to extend his stay with a club he feels is on the up both on and off the field.
"I think it's brilliant that the club has shown faith in me and offered me this deal and I'm delighted to sign it," Tomkins told West Ham's official website.
"I've been here since I was seven and this is a long-term deal which is going to take me up until I'm in my thirties, so it's nice to commit my future here.
"Being a West Ham fan, I want to spend my future here as it is exciting times with the Olympic Stadium move coming up in 2016.
"The club is going in the direction I wanted it to go and I want to be involved in. It's exciting all-round, for the club and for me."
