The 62-year-old former Republic of Ireland international made more than 300 appearances as a goalkeeper for the Saddlers before joining the backroom staff in 2008 following the departure of then goalkeeper coach Eric McManus.
He announced his retirement from his full-time role at the Banks's Stadium on Monday, but Kearns will stay on in the role of matchday host and Smith had nothing but positive words for his former colleague and friend.
"He's Walsall through-and-through and he's been a real help to me since I have been manager," Smith told the club's official website.
"As a person he commands so much respect around the club; the goalkeepers that he worked with last season spoke very highly of him and he was instrumental in the outstanding development of Jimmy Walker.
"Mick is a dear friend and whilst I wish him a happy retirement, I am delighted that he will remain involved with the club and look forward to a few more rounds of golf with him!"