Kevin Hart is at a wedding, making a toast to his best friend the groom which we see later is a lie and this what he's paid to do for a living. We then meet shy guy Doug. He's an attorney who's marrying a girl who he never dreamed would talk to him, let alone marry him. Doug does not have any friends and has no idea who he's going to get to be his best man. He also needs groomsmen. He panics! He is then introduced by his caterer to the wedding ringer Jimmy, Kevin Hart. Doug needs 7 groomsmen, something Jimmy has never done before, but at the right price agrees to do. Jimmy also finds out Doug lied to his fiance saying he (Jimmy) is a priest that's also in the military.
Jimmy enlists the help of some old friends, everyone learns their lines, and has fun in the process. Jimmy and Doug become friends. Doug marries his girl despite her suspicions that he's lying. Jimmy finds out that the bride does not really love Doug. So Doug after overhearing this confesses the whole thing was a lie, even admitting him and his wife aren't really married, as Jimmy officiated the ceremony (after the original priest was arrested) and isn't really a priest. Jimmy asks out the bride's sister, all the guys get out of there and go on the honeymoon him and his wife were going to go on.