Born and raised in Los Angeles and later Orange County, California, Jimenez moved to New York City to attend college at the School of Visual Arts.

A significant amount of Jimenez's work is related to works by George Pérez, whose art strongly influenced Jimenez. Jimenez has worked repeatedly in several Teen Titans-related series (some issues of the ongoing series New Titans and Team Titans, and the miniseries JLA/Titans, The Return of Donna Troy and Tempest), was the main artist of Infinite Crisis, a sequel of Crisis on Infinite Earths and highly related to the historical limited series, and did a large run as writer/artist of Wonder Woman (as did Perez in the 1980s). Jimenez and Pérez also have worked together in 2005-2006 in the miniseries Infinite Crisis (where Jimenez was the main penciller, and Pérez drew some sequences and covers for the series) and DC Special: The Return of Donna Troy (written by Jimenez and inked by Pérez).

Jimenez began working at DC Comics when he was 21; his first published work was four pages in the DC miniseries War of the Gods (1991).

It was announced at the 2007 San Diego ComicCon that Jimenez had signed an exclusive contract with Marvel Comics. He was one of the four artists working on Marvel's flagship title, The Amazing Spider-Man, the company's sole Spider-Man title, in which Marvel upped its frequency of publication to three issues monthly, and inaugurated the series with the "back to basics" story arc "Brand New Day" at the beginning of 2008. His first work on Spider-Man was in the Free Comic Book Day 2007: Spider-Man #1 (June 2007) comic book, with writer Dan Slott, which served as a prelude to Brand New Day.

In 2009 Marvel Editor-in-Chief Joe Quesada announced that Jimenez would take over the art chores on Astonishing X-Men beginning with Issue #31. In 2010 Jimenez co-wrote the book The Essential Wonder Woman Encyclopedia with John Wells through the Del Rey publishing company.

Other work

Jimenez teaches a life drawing course as part of the undergraduate cartooning program at the School of Visual Arts in Manhattan, where himself once studied.

Jimenez dedicated his work on the (1996) limited series Tempest to deceased DC editor Neal Pozner. Pozner had been the first editor to hire Jimenez, and the two subsequently had a relationship that ended when Pozner died of complications from AIDS in 1994.

Jimenez's work has appeared in the Chicago Museum of Science and Industry, on album covers, and in editorial magazines. He has been featured in Entertainment Weekly, TV Guide, The Advocate, Instinct and Out magazines.

Jimenez came out as gay in 1992, and his first open relationship was with the man who hired him at DC that same year, Neal Pozner.

DC

• Aquaman (vol. 3) Annual #1 (11-pages) (1995)
• Deathstroke, the Terminator Annual #1 (along with Gabriel Morissette) (1992)
• 52 #24 (full art), 25, 35 (among other artists) (2006—07)
• Infinite Crisis #1-7 (miniseries) (among other artists) (2005—06)
• The Invisibles #17-19 (1996)
• The Invisibles (vol. 2) #1-13 (1997—98)
• JLA/Titans #1-3 (miniseries) (1998)
• Legends of DC Universe (Teen Titans) 80-Page Giant #1 (1998)
• Legion of Super-Heroes (vol. 3) #94 (among other artists) (1997)
• Lobo #20 (1995)
• Otherworld #1-7 (2005)
• Planetary/Authority: Ruling the World (2000)
• Robin #6, 11-12 (full pencils); #13 (layouts only) (1994—95)
• Showcase '94 #5-6 (Huntress) (1994)
• Superman (vol. 2) #200 (among other artists) (2004)
• New Titans #94-96 (1993), Annual #8 (1992)
• Team Titans #1 (Terra story), #7-10, 13-14 (1992—94)
• Tempest #1-4 (miniseries) (1996—97)
• Wonder Woman (vol. 2) #164-188 (2000—03)
• Wonder Woman: Donna Troy (one-shot) (1998)
• World´s Finest: Our Worlds at War (3-pages only) (2001)

Marvel

• Amazing Spider-Man #552-554, 565-567 (2008)
• Free Comic Book Day 2007: Spider-Man #1 (2007)
• New X-Men #132, 139-141, 146-150 (2002—03)
• X-Men: Liberators #1-4 (miniseries) (1998)
• Astonishing X-Men #31-35 (2009—2010)
• Models, Inc. #1