Dillashaw, the UFC's bantamweight champion, needed to be 125 pounds on Friday morning and weighed in at 124.6 pounds. He typically weighs in at 135 pounds for a bantamweight bout.
Cejudo stepped to the scale approximately 45 minutes later. He hit his mark at 124.4 pounds, making the championship bout official.
Dillashaw (16-3) has won eight of his last nine fights, including back-to-back recent victories over former bantamweight champion Cody Garbrandt. Cejudo (13-2) claimed the UFC's flyweight belt in August by upsetting longtime division champion Demetrious Johnson. Following the win, Cejudo called for a shot at the bantamweight belt.
After negotiations with both sides, Dillashaw agreed to come down a weight class in hopes of picking up a second belt. The only UFC fighters to hold two belts simultaneously are Conor McGregor, Daniel Cormier and Amanda Nunes.