The 32-year-old mother of two is said to have agreed to take part in the film from RKO Pictures as a villain. She is the latest addition to the cast ensemble after Steinfeld and Jackson, reported Ace Showbiz.
Written by John D'Arco, the film will feature "Ender's Game" actress Steinfeld as a 16-year-old international assassin yearning for a normal adolescence.
Alba will portray Victoria Knox, who pursues Megan. Jackson has been on board to play Megan's mentor who trains her in the programme.