The Brazilian fighter pressured away at a relentless pace, establishing an edge in the striking game early on before earning the unanimous decision with scores of 50-45 across the judges' panel.
“It's such an amazing blessing,” dos Anjos said during his post-fight interview. “I'm an MMA fighter … I'm the best in the world.”
In the first round, dos Anjos utilized several body kicks, leaving Pettis' rib noticeably red. Pettis was forced to have his back against the fence most of the round, and dos Anjos pressured the defending champ while landing numerous head strikes. In the opening round's final minute, dos Anjos scored a takedown and coasted to the end of the frame.
Dos Anjos continued the pressure in the second round, giving Pettis a cut over his right eye. Following a takedown, dos Anjos worked from top position and landed various strikes while Pettis defended from his back. The challenger overwhelmed his opponent in that position through the end of the round.
The third round showed dos Anjos continuing his success on the feet, but at the same time scoring on numerous takedown attempts. Near the end of the round, dos Anjos secured his opponents back and hammered away with punches from behind.
Dos Anjos kept an aggressive pace in the fourth round, striking away at the battered champion and getting takedowns on every attempt. He scored a number of strikes near the end of the round with a flurry as Pettis covered up against the cage.
After four rounds, Pettis appeared to be on the receiving end of a one-sided beating. Dos Anjos secured takedowns on all attempts in the final round, and he again secured Pettis' back while hammering away with punches before time expired.
Following the loss, Pettis said he had no excuses and congratulated dos Anjos for the performance the new champion put on.
“First punch he threw, I couldn't see out of my right eye,” Pettis said, reflecting on dos Anjos' offense in the first round.
With the win, dos Anjos becomes the new UFC 155-pound champion, having beaten the division's last two title holders in Pettis and Benson Henderson. His last loss came against division contender Khabib Numragomedov, who is currently scheduled to fight Donald Cerrone at UFC 187 on May 23.
(Follow @Erik_Fontanez on Twitter)