Cunningham, who was sacked by Saints in April after a poor start to the Betfred Super League campaign, has joined the Centurions until the end of the season, the club have announced.
The 40-year-old will take over the head of rugby duties of club owner Derek Beaumont and will offer support to coach Neil Jukes.
Cunningham said: "I have not come in to take anyone's place but to add my knowledge and experience at this stage of the season. I get on well with 'Jukesy' and he is a good friend.
"Derek has brought me in to ease the burden on Neil and bring my experience to Leigh Centurions. Hopefully I will bring a new set of eyes and structures and I'm delighted to have been given this opportunity."
The Centurions were promoted to the top flight last season but face the prospect of an immediate return to the Kingstone Press Championship having failed to make the top eight and been drawn into the Qualifiers.
They began their challenge in the 'middle eight' competition with victory over Featherstone Rovers but, potentially crucially, lost to another of the Championship sides in Hull KR on Saturday.
Cunningham will be involved for the final five matches of the competition, plus the 'Million Pound Game', should Leigh be involved.
Beaumont said: "Keiron has substantially more experience than myself and I feel his appointment will bring in someone with a fresh pair of eyes and a different approach as well as a different voice around the place to freshen things up.
"I still have the utmost confidence in Neil Jukes and my coaching team and their ability to achieve our goals, which I believe will be increased by Keiron's presence."
Cunningham's assignment will not see him come up against St Helens, the club with which he is so closely associated having made 496 appearances in a stellar playing career and where a statue stands in his honour.