Lee got his start in the industry in 1987 as an artist for Marvel Comics, illustrating titles such as Alpha Flight and The Punisher War Journal before becoming widely popular through his work on The Uncanny X-Men.

Aside from illustrating comics, he has done work as a designer or creative director on other DC products, such as action figures, video games, branded automobiles and backpacks.

Outside the comics industry, Lee has designed album covers, as well as the packaging of one of General Mills' monster-themed cereal boxes for its 2014 Halloween collection.

[2][3] In a December 2023 interview, he describes his nostaglic memories of life in that country, where he first began drawing at a young age, using oil pastels with an art teacher who visited his home, and developing a love of Max Fleischer's 1940s animated Superman series.

His strongest memory of living in Seoul, however, was when, at the age of 4 or 5, he was hit by a small truck while crossing the street, later regaining consciousness in the hospital in the presence of his father, a doctor.

[5][6] Lee says that he benefited as an artist by connecting with characters that were themselves disenfranchised, like Spider-Man, or who were born of such backgrounds, such as Superman, who was created by two Jewish men from Cleveland to lift their spirits during the Depression.

[6] After obtaining his psychology degree,[9] Lee, having grown to view a career in medicine to long escalator ride that he did not wish to make,[4] decided to postpone applying to medical school for one year, in order to give himself time to break into comics.

[4] Earning the reluctant blessing of his parents, Lee vowed that he would attend medical school if he did not break into the comic book industry in the gap year he allotted for himself.

[6] He set up a small drafting table next to his bed, and would spend 8 to 10 hours each day drawing, to the point that he suffered from sore knuckles and a pinched nerve that required his father to give him a shoulder brace.

Goodwin invited Lee to Marvel Comics, where the aspiring artist received his first assignment by editor Carl Potts, who hired him to pencil the mid-list series Alpha Flight, seguéing from that title in 1989 to Punisher: War Journal.

[6][10] Lee's work on the Punisher: War Journal was inspired by artists such as Frank Miller, David Ross, Kevin Nowlan, and Whilce Portacio, as well as Japanese manga.

Enticed by the idea of being able to exert more control over his own work, in 1992, Lee accepted the invitation to join six other artists who broke away from Marvel to form Image Comics, which would publish their creator-owned titles.

Lee himself wrote and illustrated a 12-issue series called Divine Right: The Adventures of Max Faraday, in which an internet slacker inadvertently manages to download the secrets of the universe, and is thrown into a wild fantasy world.

[30] In 2005, Lee teamed with Frank Miller on All Star Batman & Robin, the Boy Wonder,[31] a series plagued by delays, including a one-year gap between the releases of the fourth and fifth issues.

Lee himself took full responsibility for the delays, explaining that his involvement with the DC Universe Online video game were the cause, and not Miller's scripts, which had been completed for some time.

[32][33][34] All-Star also drew controversy[35][36] for Miller's dialogue, pacing and depiction of the characters,[37] garnering reviews that were mixed[38] to negative,[37][39][40] though Lee's art was praised,[37] and the book enjoyed excellent sales.

12 drew media attention for its depiction of Superman and Wonder Woman in a passionate embrace, a rendition that Lee said was inspired by Gustav Klimt's painting The Kiss and Alfred Eisenstaedt's 1945 photograph V-J Day in Times Square.

Lee and DiDio presented the contestants with that episode's challenge, to create a new superhero, with six DC Comics artists on hand to help them develop their ideas.

[59] In October 2012, DC Entertainment and Kia Motors America entered a partnership to benefit We Can Be Heroes, a campaign dedicated to fighting hunger in the Horn of Africa.

[71] November 2015 saw the debut of the miniseries Batman: Europa, on which Lee collaborated with writers Brian Azzarello and Matteo Casali and artist Giuseppe Camuncoli.

[78] In 2016, Lee was the main artist on the one-shot Harley Quinn and the Suicide Squad April Fool's Special sharing art duties on that book with Sean Galloway.

[80] In March 2018, Lee and writer James Tynion IV launched the series The Immortal Men as part of DC's New Age of Heroes line.

[85] On June 5, 2019, Lee and the fashion accessory brand HEX launched a Kickstarter crowdfunding campaign for two Batman-branded backpacks designed specifically for comics artists and collectors.

[90] On November 25, 2021, Lee appeared alongside several other Asian and Pacific Islander celebrities, including actor Simu Liu, tennis player Naomi Osaka, and Top Chef host Padma Lakshmi, in the Thanksgiving Day television program See Us Coming Together: A Sesame Street Special.

The special premiered on HBO Max, PBSKids, Facebook, Instagram, and YouTube, as part of the Sesame Workshop's "Coming Together" initiative, which endeavors to educate children about race, culture, and racial justice.

I don't know how old Jim is, I presume he's young, and apart from admiring his wonderful technique — even though it's a trifle overdone; it makes my stuff look like simplicity — I just love the fabulous style that he does it with.

[95][97] A majority of the comics industry expressed support on social media for Lee's right to charge these prices including Bengal, Tom Taylor, Fabian Nicieza, and Mark Brooks.

[107] On Twitter, comic book writer, Gail Simone shared a story of how Lee drew free charity sketches in order to cover John Ostrander's eye surgery.

Lee purchased the art at a Sotheby's auction via Barry Geller, the producer of the faux film, who was selling it to help pay for his child's college tuition.

The CIA operation that rescued the Americans remained classified for another 17 years, and thus Lee had no idea of the pages' historical significance, nor did Geller know their true monetary value when he sold them to help pay his son's college tuition (with Kirby's permission).