Stevens amassed almost 17,000 runs and took 591 wickets in first-class matches during a career which began in 1997 with Leicestershire.
He moved to Kent in 2005 and played there for the rest of his career, winning five trophies, including two T20 Blast titles.
In total, Stevens made 45 centuries and 146 half centuries in 25 years as a professional player.
Pakistani former batter Jaahid Alli also joins the club as batting coach, while former academy and women’s coach Sam Faulkner will take charge of the bowlers in a coaching shake-up which has seen Toby Radford and Robbie Joseph leave the club.
“With Sam and Jaahid, there will be clear guidance and mentoring for our young talent at first-team, academy and pathway level to make any transition to a higher level more seamless from a playing perspective,” Cook added.
“Both Sam and Jaahid have worked closely with our talent pathway for a number of years now and are both held in high regard by our pathway players and staff.”