Villamor turned professional in 1989 along with his contemporaries were Andy Tabanas, Gerry Peñalosa, Rey Cosep and the Alfante brothers.
During that time he was regarded as the rising star Filipino boxer who had hopes of becoming a future world champion.
He had the opportunity to challenge the world champion for the first time with Thailand's Ratanapol Sor Vorapin, the IBF mini flyweight title holder on June 27, 1993 at Nimibutr Stadium, National Stadium, Bangkok, Thailand.
He lost TKO in the seventh round, Sor Vorapin retained title for the second time, Villamor suffered his first defeat.
Villamor had the opportunity to challenge for world title for the second time with the WBC strawweight champion the undefeated Mexican Ricardo López on March 16, 1996 at MGM Grand Garden Arena, Paradise, Nevada, U.S. As a result, he lost TKO in the early eighth round with López's left uppercut.