Born in Mazatlán, Sinaloa, Ramírez moved from Mexico to the United States at eight years old, eventually graduating with a fine arts degree from the Juilliard School.

Ramírez began acting in Broadway productions, making their[a] debut in Paul Simon's The Capeman, and later ventured into film and television roles.

[b] Ramírez's volunteered addition of the character's bisexuality marked one of the earliest series regular queer roles on primetime television.

[3][4] Ramírez's interest in music encouraged their mother to send them to San Diego School of Creative and Performing Arts, where their singing talent was discovered during an audition.

[5] After roles in the plays Into the Woods, Hello, Dolly!, and Annie,[5] Ramírez was recommended to study drama at Juilliard School, from which they graduated with a Bachelor of Fine Arts.

[7] While still at Juilliard, Ramírez was discovered by a casting director and was offered the role of Wahzinak in Paul Simon's 1998 Broadway musical The Capeman.

[8] Based on the life of the Puerto Rican gangster Salvador Agron, the production garnered negative reviews, but Ramírez was singled out for their "outstanding" performance.

[10] Starring Tom Hanks and Meg Ryan, the film had Ramírez play Rose, a Zabar's cashier who was "very serious about her line's cash-only policy.

The game was a guitar-based spin-off of PaRappa the Rapper, exclusive to Sony's PlayStation console, involving Lammy getting to her band's concert within a tight fifteen-minute window.

Charles Isherwood of Variety praised their "beautiful, smoky voice" but was critical of their "torchy" performance of "The Man I Love," which ignored "the wry irony that infuses Ira's lyrics".

[17] During this time, Ramírez also appeared in guest roles in several television series, including NYPD Blue, Law & Order: SVU, Third Watch, and Spin City among others.

[24] After success on Broadway, Ramírez joined the cast of the ABC medical drama Grey's Anatomy in a recurring role as Dr. Calliope 'Callie' Torres, a love interest for Dr. George O'Malley, in the show's second season.

[28] Ramírez, who was initially given a recurring status at the time of the character's inception, received a star billing in the show's third season, alongside fellow cast member Eric Dane, who portrayed Dr. Mark Sloan.

[29] Ramírez provided a cappella vocals in the song "Silent Night" for the soundtrack of the show's sixth-season episode "Holidaze," airing on November 19, 2009.

Marcus James Dixon of Gold Derby called them the "show-stopper" and wrote that they "stole the show in a gut-wrenching performance worthy of an Emmy award.

[31] Maggie Fremont, a TV critic for Vulture, reviewed Ramírez and Jessica Capshaw's performances during an 11th season episode, calling them "goddesses walking amongst mere mortals".

"[37] Rhimes wrote of Ramírez's work on the show, "Dr. Callie Torres came into our lives dancing it out in her underwear almost a decade ago, and I could not be happier or more proud of her journey.

[39] From 2017 to 2019, Ramírez co-starred in the fourth and fifth seasons of the CBS political drama Madam Secretary, replacing Bebe Neuwirth, who played Nadine Tolliver.

[45] In June 2024, Ramírez filed for divorce from Ryan DeBolt, three years after announcing the couple's separation, citing irreconcilable differences as reason for the split.