The nonexclusive agreement was signed one month ago and is the first time the London-based law firm has signed a referral agreement in India's coveted legal market.
"Previously, the firm has referred clients to a number of different Indian firms but this is not in the clients' best interest," said Alex Pease, head of Allen & Overy's India group.
"The aim is to get to a stage where we give the best possible service to Indian clients. We want them to have the best quality of service, as well as the service which is most similar to the one we would give," Pease said.
"[Trilegal] is organized on western lines," added Pease. "We chose them because they are a young -- none of their lawyers is older than 40 -- up and coming, energetic firm."
The top five London firm will also provide Trilegal with training and back-office support.