In March 2011, it was announced that Griffin had signed a two-year senior deal with the province and would be part of the first team squad for the coming season. Connacht played in the Heineken Cup for the first time in the 2011–12 competition, with Griffin playing in three of the province's six games. He started in the away match with Harlequins, the home match with Toulouse and the away match against Gloucester. He also made 11 starts and four substitute appearances in that year's league.