He defeated Bangsaen Sithpraprom for the World Boxing Foundation (WBFo) super flyweight title on 7 November 2004.

The younger fighter appeared to be in control of the match in the early rounds, as he skillfully kept the much shorter Peñalosa away with crisp jabs.

[5] After the Manny Pacquiao-Marco Antonio Barrera rematch in Las Vegas, Peñalosa and Jorge Arce of Mexico nearly figured in a fistfight, according to a report by Philboxing.com.

Peñalosa was reportedly with his wife Goody and Japanese associate Kosuke Washio when the incident happened.

The proud Mexican, the report said, apparently did not like the comments and immediately confronted the Filipino world champion.

According to the report, Peñalosa was apparently irked by Arce's actuations and tried to follow the Mexican boxer but was prevailed upon by Goody.

Early in the fight, both pugilists exchanged combinations, with López gaining a slight advantage by targeting the head and body of Peñalosa.

During the following two rounds, López managed to establish control of the offensive's tempo, but Peñalosa continued using his counterattack.

Prior to the ninth chapter, Peñalosa's trainer, Freddie Roach, warned him that he had to win by knockout or the fight would be stopped.

Many people, including members of his family and his friend, Manny Pacquiao, wanted Peñalosa to quit boxing already, saying he has nothing more to prove in the sport.

[8][9] In April, Peñalosa was stripped of his bantamweight title before challenging WBO junior featherweight champion Juan Manuel López.

Many tough boxers were considered to be his possible next opponent, including Jorge Arce, Daniel Ponce de Leon, Eric Morel and Vic Darchinyan.

The veteran fighter trained at the Wild Card Gym in Los Angeles under the guidance of coach Freddie Roach, along with Filipino prospect Bernabe Concepcion and seven-division world champion Manny Pacquiao.

[14][15] At the opening round the Puerto Rican looked to stick and move while Peñalosa took on the role of the aggressor.

The injury bled profusely during the next rounds, but he was able to hurt the opponent with strong body punches and seemed to take control of the fight.

[17] Some people even said that the Filipino boxer should have won over the Puerto Rican, including his trainer, Freddie Roach, and Manny Pacquiao.

[22] On April 21, 2008, Peñalosa won in the game show Wheel of Fortune held in the Philippines, defeating fellow boxers Rey Bautista and Alex John Banal.