His first professional championship was the Puerto Rican flyweight title, which won by defeating José Luis De Jesús.

López's first championship opportunity was against Alberto Jiménez for the World Boxing Organization's flyweight title, in a contest that he lost by unanimous decision.

Subsequently, López defeated Daniel Pérez, Melquiades Ventura, José Ayala and Victor Cruz before losing to Andy Agosto by points.

[1] He would defeat Miguel Santos, Martin Solorio, José Luis Zepeda and Fernando Valencia by knockout before receiving a second opportunity for the organism's championship.

[3] After defeating Iván Salazar and Rafael Orozco by knockout, López moved up one division to challenge Mauricio Pastrana for the International Boxing Association's super flyweight championship, but lost by unanimous decision.

[4] On June 23, 2001, López defeated Javier Cintrón by technical knockout to win the WBO Latino super flyweight title.

In this contest, López defeated Everardo Morales by unanimous decision, winning the WBO Latino flyweight championship.

He challenged Juan Mercedes for the WBO Latino super flyweight title, defeating him by technical knockout in four rounds.

On October 4, 2008, López defended the WBO Latino super flyweight title for the first time, defeating Jonathan Pérez by technical knockout in seven rounds.

However, Bob Arum, Montiel's promoter, announced on January 8, 2009, that he was having difficulty to make the flyweight limit, choosing to vacate the championship.

The card, which was held at the Coliseo Rubén Rodríguez in Bayamón, marked the first time that López fought for a world championship in Puerto Rico.

[16] After eleven months of inactivity, López returned to activity against fellow Puerto Rican and the International Boxing Organization's flyweight champion, César Seda Jr., at a catch weight.