[5] On January 18, 1985, Ricardo made his professional debut at the age of 18 by scoring a third-round knockout of Rogelio Hernandez.
On October 10, 1990, López defeated WBC and lineal mini flyweight champion Hideyuki Ohashi of Japan via fifth-round knockout to win his first world title.
In 1992, he defended his title against Pretty Boy Lucas (22–2–2) of the Philippines via Unanimous Decision and Rocky Lin (14–0) of Taiwan via TKO.
López started 1993 with a stoppage victory over amateur standout Kwang-Soo Oh and followed it with a knockout over future two-time champion Saman Sorjaturong of Thailand.
After López won the WBO title, he said he wanted to give his championship belt to his father, who is a boxing fan.
His statement to Mexican newspapers prompted the organization to take away López' title and sanction a match between Eric Jamili and Mickey Cantwell to fill the vacancy.
On March 7, 1998, López fought undefeated WBA mini flyweight champion Rosendo Álvarez to a technical draw after referee Arthur Mercante Sr. stopped the contest following an accidental clash of heads in the seventh round.
This fight was part of undercard featured Julio César Chávez vs. Miguel Ángel González for the vacant WBC super lightweight title.
[15] Ricardo "El Finito" López was voted as the greatest Strawweight and Light Flyweight Champion ever by the Houston Boxing Hall Of Fame in 2014, while BoxRec rates him the best Minimumweight of all time.