Pires, who turns 41 in October, has not played professionally since a brief spell with Aston Villa came to an end three years ago.
A World Cup winner with France in 1998, he is best known for a hugely successful six-year stint at Arsenal, which saw him play an integral part in securing two Premier League titles and three FA Cup winners' medals.
He will now follow the likes of Luis Garcia and Joan Capdevila in participating in India's new competition, scheduled to run from October to December.
It has yet to be confirmed which team Pires will represent, but he expressed his excitement at the challenge that awaits.
He told the ISL's official Twitter account: "I am sure the Indian Super League will be a huge success and I am delighted to be part of it."
Freddie Ljungberg, a former team-mate of Pires at Arsenal, signed up for an ambassadorial role with the ISL last week.