Lampard, Chelsea's all-time top scorer, signed a three-year contract with the English side after he secured his release from his previous club, Derby County, reports Efe news.
"I am immensely proud to be returning to Chelsea as head coach," the 41-year-old said, according to the club's official website.
"Everyone knows my love for this club and the history we have shared, however, my sole focus is on the job in hand and preparing for the season ahead. I am here to work hard, bring further success to the club and I cannot wait to get started," he added.
Lampard, who led Derby to the Championship play-offs last year, returned to Stamford Bridge after the departure of previous coach Maurizio Sarri.
The Essex-born player first joined Chelsea from West Ham in June 2001 for 11 million pounds and spent 13 seasons there.
He made 648 match appearances and became the club's record scorer with 211 goals.
Chelsea director Marina Granovskaia pointed out that Lampard "possesses fantastic knowledge and understanding of the club and last season he demonstrated he is one of the most talented young coaches in the game."
"After 13 years with us as a player, where he became a club legend and our record goalscorer, we believe this is the perfect time for him to return and are delighted he has done so," she added.
The former midfielder won the 2012 UEFA Champions League, three Premier League crowns in 2005, 2006 and 2010, the 2013 UEFA Europa League, two League Cups in 2005 and 2007, four FA Cups in 2007, 2009, 2010 and 2012 and two Community Shield trophies in 2005 and 2009.
( With inputs from IANS )