Martínez was born in New York City on January 2, 1963, to José and Christina Salgado Martinez, who were from Puerto Rico.

His brother and sister returned to New York to live with their parents, but Edgar opted to remain in Dorado with his grandparents.

He played semiprofessional baseball and worked two jobs, as a supervisor in a furniture store by day and in a General Electric factory at night.

[5] At the suggestion of the owner of his semiprofessional team, Martínez attended a tryout held by the Seattle Mariners of Major League Baseball (MLB).

[5][7] He initially considered declining the offer, due to the money he was making in Puerto Rico, but Carmelo convinced him to sign.

[2][8] The scout who signed Martínez convinced Hal Keller, the Mariners' general manager, to assign him to the Arizona Instructional League (AIL) after the season.

Keller did not believe Martínez would be able to hit in the major leagues, and initially did not want to assign him to the AIL, which is reserved for the best prospects.

[10] Martínez made his major league debut on September 12, 1987, as a third baseman, and proceeded to hit .372 over his first 13 career games.

He also tied Frank Thomas for the most doubles in MLB,[18] and set a team record for most in a season (this has since been surpassed by Alex Rodriguez).

[20] During an exhibition game at BC Place Stadium in Vancouver, British Columbia, before the 1993 season, Martínez tore his hamstring on an unzipped seam in the turf between first and second base.

In 1994, in his first plate appearance of the season, opposing pitcher Dennis Martínez hit him in the right wrist,[22] and he was placed on the disabled list.

[19][24] He also finished third in AL Most Valuable Player Award voting behind Mo Vaughn and Albert Belle.

[26] In the 1995 American League Division Series (ALDS) against the New York Yankees, Martínez hit .571 and was on base 18 times in five games.

The Mariners' 1995 postseason run helped build the groundswell of public support that led the Washington State Legislature to enact legislation to fund a dedicated baseball stadium in Seattle to replace the Kingdome.

Mariners' manager Lou Piniella referred to it as "the hit, the run, the game, the series and the season that saved baseball in Seattle.

Martínez was selected to the 1997 MLB All-Star Game and won the Silver Slugger Award at the end of the 1997 season.

[2] The Mariners reached the postseason, and Martínez batted .364 in the 2000 ALDS, defeating the Chicago White Sox.

[7] Seattle tied the major league record set by the 1906 Chicago Cubs with 116 wins on the season.

Martínez hit .313 with two home runs in the 2001 ALDS as Seattle defeated Cleveland, but he batted .150 in the 2001 ALCS as they lost to the Yankees.

[7] The Mariners struggled, falling out of the postseason chase, and the team began to give playing time at designated hitter to Bucky Jacobsen.

[42] At his retirement ceremony, a portrait "featuring his high stepping batting style" painted by artist Michele Rushworth was presented to him by the Mariners.

While some sports writers felt that his batting numbers do not overcome the one-dimensional aspect of his career as a DH, others have compared this to the specialty of closers whose contribution to their teams victories resides on working one inning to preserve an advantage and the fact that these late inning relievers are not involved in other facets of the game such as hitting and base running.

[52] He entered the Hall with the aforementioned Rivera, who was elected in his 1st year of eligibility, along with the late Roy Halladay (1st ballot, posthumous).

The Complejo Deportivo Edgar Martinez,[53] named after Martínez, was built in barrio Higuillar in Dorado.

Sustaining structural damages as a result of Hurricanes Maria and Irma in 2017, a $700,000 restoration of the sports complex was completed in 2021.

[57] Following the firing of Jarret DeHart on August 22, 2024, the Mariners announced that Martínez would be serving as the team's hitting coach for the remainder of the season.

[61] Martínez and his wife Holli have contributed their time and money to Seattle Children's Hospital, including the Edgar Martínez Endowment for Muscular Dystrophy Research, established by the Mariners in honor of his retirement, and the Children's Hospital Annual Wishing Well Night at T-Mobile Park.

Martínez has also supported the Parent Project Muscular Dystrophy, Overlake Hospital, Make-A-Wish Foundation, Wishing Star Foundation, United Way, Esperanza, Page Ahead Children's Literacy Program, Big Brothers Big Sisters, Boys & Girls Clubs of America, and Mariners Care.

Because of his contributions, on June 20, 2007, Martínez was inducted into the World Sports Humanitarian Hall of Fame in Boise, Idaho.

[64] For the 2013 season, the Mariners worked with Martínez, local chef Ethan Stowell and bartender Anu Apte to create "Edgar's Cantina" at T-Mobile Park.