The 43-year-old had been assistant coach at Canterbury since the start of the 2014 campaign, working under Jimmy Adams, who left the club in October.
Former South Africa fast bowler Allan Donald, who played 72 Tests for the Proteas between 1992 and 2002, has been confirmed as Walker's assistant.
"It's a great opportunity and hopefully it will be a natural progression," Walker told BBC Radio Kent.
"I'm proud and honoured to be given the role."
Walker spent 16 seasons as a Kent player, scoring over 15,000 runs for the county, before moving to Essex at the end of 2008.
Adams spent five years as head coach but departed at the end of last season, after Kent finished second in the Division Two table and missed out on promotion.
"I know how the club operates, what is expected and what it means to play for the club," Walker added.
"In the last couple of years we have slowly moved the club forward and seen improvements.
"As a head coach coming in, the aspiration has to be winning titles. I am ambitious and so is the group."
Donald has been part of the Australia, New Zealand, South Africa and England coaching teams and worked for Warwickshire and IPL franchise Royal Challengers Bangalore.
"I would like to thank the club for giving me this opportunity to work with this very talented group as the assistant coach," the 50-year-old said.
"There is no doubt that I'm pumped for the new season ahead and can't wait to meet all the players and backroom staff."
Kent have appointed former player Matt Walker as the club's new head coach.