Kremer was born in the Bronx, the son of a sign painter. He counted Alex Raymond's Flash Gordon and Hal Foster's Prince Valiant among his influences.

He graduated from the High School of Music and Art and the School of Industrial Arts in New York City. Kremer then did layout, lettering, and illustrations for pulp and aviation magazines for ten years. He gradually took on more comics work in Ace Publications, his first title being "Hap Hazard". He married that title's letterer, Grace. Due to a hernia, Kremer did not serve in World War II.

Steve Mufatti, a friend and colleague of Kremer's, had a part in getting him work at Harvey Comics, starting with freelance work in 1948. With Alfred Harvey, publisher, and editor Sid Jacobson.

Mr. Jacobson was frustrated by the poor design of most comics at the time. He watched animated films, and wanted to know why his comics couldn't look as good. So, Warren was brought onboard to bring an animation design to comics. Mr. Kremer improved the layout of the panels, creating a much greater depth of field. His characters were better constructed, which added mass and allowed the books to look more "real". Eventually, his influence was felt though out the entire comic book industry.

Kremer created or defined many of the most well-known Harvey characters, including Casper, [[Hot Stuff the Little Devil|Hot Stuff]], [[Joe Palooka]],  [[Little Audrey]], [[Little Max]], [[Richie Rich]], and [[Stumbo the Giant]].  Kremer also excelled at realistic treatments, producing top-quality work for Harvey's romance, war, and horror genre titles. He was the top artist at Harvey, where he worked for 35 years mostly as an Art Editor.

In addition to his regular pencilling, Kremer contributed animation storyboards, pencilled, inked and coloured most of the thousands of covers for every one of Harvey's humour titles. According to Sid Jacobson, Kremer could produce 8 pages of interior pencils a day at his most productive. Artists in the Harvey humor department were instructed to emulate Kremer's style as closely as they could.

After Harvey ended publication in 1982, Kremer created and/or drew several characters for Marvel Comics' Star Comics line, including Count Duckula, Ewoks, Planet Terry, Royal Roy, and Top Dog. In 1989, a stroke left him paralyzed on his left side, which included his drawing hand. He attempted to use his right hand, but was so discouraged with the results that he stopped drawing altogether.

Kremer lived in Bloomfield, N.J., and died in a hospital Glen Ridge, N.J. following a short illness. He was survived by his wife, Grace, two sons, Richard W. (after whom Richie Rich was named) and Peter R.; two daughters, Maryanne Kremer-Ames and Suzanne Petrozzino; a sister, Anita Sudol; and two grandchildren.

Artist Marie Severin remarked upon a visit Kremer made to the Marvel Comics bullpen "They don't know it, but this is the best artist who ever walked through these doors." Animator Martin Taras said "You know, if Warren went into animation, we'd all have to leave our jobs!"

Digital

• Flat Earth! - Warren Kremer
• Lambiek.net - Warren Kremer
• Scoop - In Memoriam: Warren Kremer