The 65-year-old, who was sacked by Spurs in June, began his managerial career with the Cherries in 1983.
He left Dean Court in 1992 but is now rejoining the club on a voluntary basis.
A statement on the club's website said: "Former manager Harry Redknapp has taken up an advisory role at the Goldsands Stadium.
"Redknapp will not have an official title but will offer his advice and expertise to all aspects of the club.
"The former Portsmouth, West Ham and Tottenham boss will also travel with the Cherries squad to Huish Park tomorrow as they take on second placed Yeovil."
Chairman Eddie Mitchell added: "I met Harry for a chat this morning and he offered to come in on a voluntary basis.
"He still has a passion for the club and for football, and he's got too much to offer for us to let him slip through our fingers.
"It's been in my mind for quite some time to get him involved, and the timing seems to be perfect for us to tap into his knowledge."
Bournemouth are currently 19th in the League One table, having drawn three of their opening four matches.