The White Collar actor will play Blaine's (Darren Criss) older brother Cooper in the Fox musical show's next instalment on April 10.
Bomer is expected to duet with Criss on a mash-up of Duran Duran songs in the episode, which is titled 'Big Brother'.
Insiders have claimed that their performance "will be very sexy and fun and big".
Melrose Place actor Thomas Calabro signed up to play the father of Puck (Mark Salling) last week.
Glee airs in the UK Thursdays at 9pm on Sky1.
> 'Glee': Fox co-chair teases "powerful" finale, "exciting" season four