Hayek will reprise her role as Elisa Padriera, Alec Baldwin's former fiancee, a character she played over six episodes in 2009, reported Huffington Post online.
No word on whether the pair will re-ignite their romance, but if so, Baldwin's Donaghy will have his hands full.
Also returning for the series send-off is Julianne Moore, who played former Donaghy flame Nancy Donovan on the series for a handful of episodes in 2009 and 2010.
Hayek is the latest guest star to sign on for the '30 Rock' swan song.
Congresswoman Nancy Pelosi and rapper-Law & Order: SVU" star Ice-T have also signed on for the farewell extravaganza.
'30 Rock', which is currently winding up its seventh season, airs its finale on January 31.