"Friends, I don't know if you have heard, but it's going down in August, close to home in Milwaukee. Cannot wait," Guida, a native of Round Lake, Ill., tweeted.
Guida and Mendes were originally scheduled to fight April 20 in San Jose, Calif. But Guida suffered an undisclosed injury and withdrew from the bout.
Darren Elkins replaced Guida at the UFC on Fox 7 event and was knocked out in the first round by Mendes, who has a professional record of 14-1.
Mendes, who was KO'd in the first round by champion Jose Aldo during a January 2012 title bout, has won three fights in a row. He has knocked out each of his opponents in the opening round during the streak.
Guida, who made his featherweight debut in January with a split decision over Hatsu Hioki, seeks his second straight win in the division. The former lightweight contender is 30-13.
Poirier and Koch will attempt to get back in the win column. The two were scheduled to meet in February 2012 at UFC 143, but an injury forced Koch to withdraw.
In his most recent bout Feb. 16 in London, Poirier dropped to 13-3 after a unanimous decision loss to Cub Swanson.
Kock (13-2) was knocked out on Jan. 26 in the second round by Ricardo Lamas. He was scheduled to fight Aldo for the featherweight title in October 2012, but a partially torn medial collateral ligament in his right knee forced Koch to withdraw from the bout.
It was the second time a title fight with Aldo failed to materialize for Koch, who is trained by Duke Roufus in Milwaukee. Aldo pulled out of their July 2012 showdown with an undisclosed injury.