© Rex Features / Sara Jaye
The 40 Year Old Virgin actor will play Ryan - the father of Kristin's infant son - in season two of the ABC comedy, TV Guide reports.
Masterson replaces popstar Nick Jonas, who played the role in last year's Christmas episode.
His previous credits include a role on ABC Family's Greek and guest stints on CSI: Miami and How I Met Your Mother.
The part of Kristin - the daughter of Mike Baxter (Allen) - will also be recast for season two, with Amanda Fuller (Grey's Anatomy) assuming the role previously played by Alexandra Krosney.
Last Man Standing returns to ABC on November 2.
> Tim Allen's Last Man Standing gets new showrunner
> ABC unveils fall premiere dates: Modern Family, Last Resort, Revenge
Watch a trailer for Last Man Standing below:
