The 59-year-old comes in to the London Stadium after former first-team coach Stuart Pearce stepped down from his role.
Warburton previously managed Brentford, Rangers, Nottingham Forest and QPR and even led the the west London side to a top-half finish in the Championship last season before leaving the club this summer after three seasons in charge.
He will take up his new role when the Hammers return for pre-season training at the weekend and will join Billy McKinlay, Paul Nevin, Kevin Nolan and Xavi Valero on David Moyes' coaching team.
Warburton said: "It's a huge privilege to be joining West Ham United to work as part of David Moyes' backroom staff.
"West Ham have made incredible progress in recent seasons, continually making forward strides to move the club in a positive direction.
"I am excited about coming in and adding my own experience and know-how to what is an incredibly strong coaching team here."
Moyes added: "I'm really pleased to welcome Mark to West Ham United. He's a really valuable addition to the backroom team, in the wake of Stuart Pearce leaving us at the end of last season.
"Mark is hugely experienced and has a fine track record, having managed at a number of Club's over the course of his career.
"I'm excited about adding him to my coaching set-up as one of my assistants."