Marie Severin grew up in an artistic household where her father, a World War I veteran, eventually became a designer for the fashion company Elizabeth Arden during the 1930s. In her teens, Severin took "a couple of months" of cartooning and illustration classes, and attended Pratt Institute in Brooklyn, New York "for one day and said, 'This is a college', and I wanted to draw and make money".
Severin was working on Wall Street when her comics-artist brother, John Severin, needed a colorist for his work at EC Comics. Marie Severin's earliest recorded comic-book work is coloring EC Comics' A Moon, a Girl...Romance #9 (Oct. 1949). She would contribute across the company's line, including its war comics and its celebrated but notoriously graphic horror comics, for which she sometimes gave especially gruesome panels a single color in order to tone down otherwise graphic scenes of gore.
At EC, Severin worked on the comics' production end, as well as "doing little touch ups and stuff" on the art. When EC ceased publication in the wake of the U.S. Senate hearings on the effects of comic books on children and the establishment of the Comics Code, Severin worked briefly for Marvel Comics' 1950s predecessor, Atlas Comics, until an industry downturn circa 1957 prompted her to seek work with the Federal Reserve Bank of New York. She recalled in 2001, "I did a little bit of everything for them — I did television graphics on economics [and] I did a lot of drawing. I did a[n educational] comic book that my brother did the finished art on ... about checks".
In 1959, when the industry had picked up again to during the period fans and historians call the Silver Age of comic books, Severin again worked for Marvel Comics in production. Severin recalled in 2001 that when Esquire magazine requested an artist to illustrate a story "on the college drug culture", Marvel production manager Sol Brodsky offered Severin rather than one of the regular artists, all on deadline. Her illustration for the magazine led to Marvel editor-in-chief Stan Lee assigning her to succeed character co-creator Steve Ditko on the feature "Doctor Strange" in Strange Tales.
Severin continued to expand from colorist to do penciling and inking, and occasionally also lettering, on various titles. She drew stories of the Sub-Mariner and the Hulk, and the covers or interiors of titles including The Amazing Spider-Man, Iron Man, Conan the Barbarian, Kull the Conqueror, The Cat, and Daredevil. Additionally, she worked on Marvel's satiric humor magazine Crazy, as well as the company's self-lampooning comic book, Not Brand Echh.
In the 1980s, Severin was assigned to Marvel's Special Projects division, which handled non-comic book licensing such as from toy maquettes, film and television tie-ins, and the short-lived children's book imprint, Marvel Books.
During the 1990s, Severin penciled the "Impossible Tale" of the "Li'l Soulsearchers" in issue #31 (Aug. 1998) of Claypool Comics' superhero-humor comic Soulsearchers and Company, inked by fellow Silver Age veteran Jim Mooney; and she inked Dave Cockrum's penciling in issue #43 (July 2000). She also inked Richard Howell's pencils on the story "Favor of the Month" in Elvira #144 (April 2005).
Severin retired sometime afterward, but continued into the mid-2000s to make occasional contributions, such as recoloring many of the comics stories reprinted in the EC-era retrospective books B. Krigstein and B. Krigstein Comics. The former won both the Harvey and Eisner comic-industry awards in 2003.
On October 11, 2007, Severin suffered a stroke, and was taken to Huntington Hospital in Huntington, New York, on Long Island, to recover and recuperate.
Severin won the Best Penciller (Humor Division) Shazam Award in 1974. The following year, she was nominated for both Best Inker (Humor Division) and Best Colorist.
Severin spoke at a 1974 New York Comic Art Convention panel on the role of women in comics, alongside Flo Steinberg, Jean Thomas (sometime-collaborator with husband Roy Thomas), Linda Fite (writer of "The Claws of the Cat" and a few other Marvel titles) and fan representative Irene Vartanoff.
Severin won an Inkpot Award at the San Diego Comic Con in 1988.