On September 14 of 1972, he began his professional boxing career with a four round decision win over Javier Martinez. His next fight, three weeks later, was against the same rival and ended up the same way. On November 16 of that year, he drew (word used in boxing for tie) with Ted Liggett in four rounds.
He won five fights, one by knockout in 1973, year after which his name was becoming more and more known in California. That might have been due to the fact that all his fights were taking place there.
In 1974, Palomino went through an increment in quality of opposition. He won six fights and lost one. He beat David Arellano twice, by a decision in ten and by knockout in nine, as well as Tommy Howard, by decision in ten, but he lost to Andy Price, who was a title contender at the time, by decision in ten in San Diego.
In 1975, he won four fights, and drew in two. He and Zovek Barajas had two bouts that year, the first one resulting in a ten round draw and the second one being a nine round knockout win for Palomino. He also drew with Hedgemon Lewis.
After winning two fights in 1976, Palomino found himself and his trainers travelling to London, where an internationally televised world championship bout awaited him against WBC world Welterweight champion John H. Stracey, a British boxing teacher who had dethroned Jose Napoles as world champion. Palomino became a world champion on the night of June 22 of that year at Wembley Arena, when a right hand of his landed on Stracey, who went down and was counted out. Many Mexicans who viewed Napoles, a Cuban born resident of Mexico, as another countryman, saw this as a revenge from Stracey.
He waited six months for his next fight, against another very popular boxer of Mexican background: cross-town rival Armando Muniz. This was a fight that had many fans guessing who'd win it for months before it happened, but it also made history in the boxing books: When Palomino and Muniz met, on January 21 of 1977, it was the first time in boxing history two college graduates met for a world title. Palomino and Muniz, now a beer salesman for an important beer company, fought what book The Ring: Boxing in the 20th. Century has described as one of the best fights of 1977. After 14 rounds, all three judges had the fight tied on their scorecards, but Palomino scored two knockdowns in the fifteenth and final round and he retained the world title by a knockout in that final round. A return to London resulted in an 11th round knockout victory over Dave Boy Green, after which he defended against Everaldo Acosta Azevedo and Jose Palacios, Azevedo being defeated by decision in fifteen and Palacios by knockout in thirteen.
In 1978, he defended his crown with a win over Ryu Sorimachi by a knockout in seven, a knockout in nine over Mimoun Mohatar, and a decision in fifteen in his long awaited rematch with Muniz.
His championship run ended in 1979, when he travelled to Puerto Rico, where he was defeated on January 13 by Wilfredo Benitez, who won a fifteen round split decision over Palomino.
In his next fight, Palomino met legendary Roberto Duran on June 22 of that year at the Madison Square Garden, in another nationally televised bout, as part of the Larry Holmes-Mike Weaver world Heavyweight championship bout's undercard. Palomino lost to Duran by decision in ten rounds, and he announced his retirement from boxing right away.
In 1980, however, Miller Lite beer, signed Palomino as a spokesman as part of a television commercial campaign that also included Walt Frazier and many other noted athletes. Palomino not only was able to keep in the public's eye as a consequence of this, but he discovered that he enjoyed acting as well, and, because of that, he decided to launch a career as an actor. He participated in a number of movies and television series, and then, in the middle 1990s, he was elected as chairman of the California State Athletic Commission, where he performed for a few years until he decided to launch a boxing comeback at the age of 38, in 1997.
Palomino began his comeback on January 10, beating Ismael Diaz by a knockout in round nine. He won four fights that year. including one over former world champion Rene Arredondo, but when he lost by decision in ten to former Oscar De La Hoya world title challenger Wilfredo Rivera on May 30 of 1998, he decided to retire for good, and has stayed in retirement ever since.
He is now involved in charity work, more particularly with Tony Baltazar's charity organization, and he travels around the United States to attend charity events and do autograph shows.
Palomino was selected to the International Boxing Hall of Fame on January 8, 2004.
He had a boxing record of 31 wins, 4 losses and 3 draws, with 19 wins by knockout