He held multiple world championships in three weight classes and is considered to be one of the greatest Puerto Rican boxers of all time.

Trinidad is frequently mentioned among the best Puerto Rican boxers of all time by sports journalists and analysts, along with Juan Laporte, Esteban De Jesús, Wilfredo Vázquez, Miguel Cotto, Wilfred Benítez, Wilfredo Gómez, Héctor Camacho, Edwin Rosario and Carlos Ortíz.

Trinidad traveled to San Diego, California, and defeated the IBF welterweight champion Maurice Blocker in two rounds, in a fight card on June 19, 1993, televised by Showtime.

[16] On September 17, 1994, Trinidad traveled to the MGM Grand for a second straight fight to compete in a title defense against Yori Boy Campas, who had a record of 56–0.

[19] Trinidad's fourth fight outside Puerto Rico or the United States took place on Estadio de Beisbol in Monterrey, Mexico.

[21] In the fourth round Trinidad connected a solid punch that injured Carr, and in the eighth he scored three consecutive knockdowns before the referee stopped the fight by technical knockout.

[23] This fight was part of a card that took place on April 3, 1998, in Bayamón, Puerto Rico and marked the first time that Trinidad had performed in the island in five years.

[23] Early in the third round a series of jabs opened a wound on Zulu's mouth, while the challenger's punches were not reaching their target.

[23] Trinidad began the fourth round heavily on in the offensive connecting several combinations which hurt the challenger, using this to land more punches in Zulu's head and body.

[23] On February 20, 1999, Trinidad defended the welterweight championship against Pernell Whitaker, winning the fight by unanimous decision in a contest that marked his thirteenth successful defense.

[24] In the spring of 1999 Don King and Oscar De la Hoya's promoter, Bob Arum, agreed to co-promote a mega-fight for the Lineal, WBC and IBF welterweight championships on September 18, 1999, at the Mandalay Bay Hotel in Las Vegas.

Early in the fight De la Hoya employed boxing to connect combinations while avoiding Trinidad's attacks.

Trinidad was having a lot of problems finding De La Hoya and couldn't connect as flush as usual with his punches, although he scored at times, Oscar's movement was not letting him land in combination and it was proclaimed by many to have been a lackluster fight.

Oscar was scoring on Trinidad but halfway through the tenth, De La Hoya stopped sticking and basically disengaged under instruction of his corner who thought the match was won.

[25] In 2000 Trinidad vacated the welterweight championships and moved to the junior middleweight division, in order to challenge the World Boxing Association's champion David Reid.

[26] On December 2, 2000, he was scheduled to fight in a unification card against Fernando Vargas, the International Boxing Federation's junior middleweight champion.

[27] The fight began in a fast pace with Trinidad connecting a solid left hook that led to his opponent being knocked down.

[27] In the fourth round's opening seconds a Vargas' short left hook connected on Trinidad's jaw and he fell on his backside getting up immediately., marking the eighth knockdown in his career.

[27] In the sixth round Trinidad regained control of the fight's tempo that lasted throughout the contest, connecting punches on Vargas' head and left jabs to the ribs.

[28] Trinidad subsequently scored a knockdown in the fourth round, during this stage of the competition he was using combinations of left hooks and right punches to the head.

After receiving assurances from Madison Square Garden officials and the City of New York, Don King rescheduled the fight for September 29.

[29] In the twelfth round Hopkins' scored a knockdown, but before the contest could continue Trinidad's father entered the ring, which led to the referee stopping the fight by technical knockout.

The Hopkins camp claimed that Trinidad's hands were wrapped incorrectly, and threatened to cancel the fight unless they were rewrapped correctly.

[30] Trinidad was subsequently scheduled to fight against Hacine Cherifi in a contest that he won by technical knockout in the fourth round.

[31] In the last minute of the round a punch by Trinidad hit Cherifi's chin leaving him disoriented, he followed this with a combination and scored a knockdown.

[33] On May 14, 2005, Trinidad competed against Winky Wright, in a fight where the winner would become the World Boxing Council's number one challenger in the Middleweight division.

[34] Trinidad's fighting style appeared to be out of rhythm in the first round, while Wright presented a defensive stance and relied on jabs.

[38] Beginning in July 2009, Trinidad became involved with the World Wrestling Council, participating as a guest referee at their anniversary show.

On September 12, 2018, judge Anthony Cuevas Ramos signed a letter which declared that the Banco Popular de Puerto Rico must pay Trinidad $2,000,000 within 24 hours, due to them owing him interest money from his personal accounts at the bank.

[40] On February 13, 2023, the Trinidads reached a confidential agreement to solve their problems with their debtors, including Banco Popular de Puerto Rico, without going to court.