During Saturday night's WEC 45, the company announced that Brown (22-5) will make his way back to the cage on Jan. 10, taking on Anthony Morrison in a bout just added to the card.
The event, WEC 46, will take place at Arco Arena in Sacramento, Calif.
Brown captured the championship in Nov. 2008 against Urijah Faber and successfully defended the belt twice, defeating Leonard Garcia and then Faber in a rematch before falling to Aldo on Nov. 18.
Morrison is just 10-7 in his career but has won four of his last five, including a win over former UFC lightweight Alvin Robinson.
WEC 46 features a lightweight title main event between champion Jamie Varner and interim belt-holder Ben Henderson.
Here are the officially announced fights for WEC 46:
Jamie Varner vs. Ben Henderson
Urijah Faber vs. Raphael Assuncao
Dave Jansen vs. Kamal Shalorus
Mike brown vs. Anthony morrison
Mackens Semerzier vs. Deividas Taurosevicius