Ranieri, who has guided the Foxes into first place on the table with nine matches remaining, coached Lampard at Stamford Bridge between 2001 and 2004.
Lampard said the Italian was a man who got the best out of him and developed him into one of the best players in England's top flight.
"I owe him everything. If it wasn't for Claudio, I wouldn't have had the career I had. I wouldn't still be playing, probably," Lampard told the Daily Mirror.
"He's got the best out of certain players. He's given hope to Jamie Vardy. We've all been waiting for that moment when Leicester go and it hasn't come.
"I'm delighted for Claudio. He deserves it for the career that he's had."