Dick Giordano, a comic book artist and former executive editor at DC Comics who helped revive longstanding comic book characters and reimagine them for new audiences, died on Saturday at the Memorial Medical Center in Daytona Beach, Fla. He was 77 and lived in Palm Coast, Fla.

The cause was complications of treatment for leukemia, Pat Bastienne, a longtime friend and colleague, said in an e-mail message.

Image Dick Giordano holds a proclamation declaring “Dick Giordano Day,” at MegaCon in Orlando in 2007. Credit... Rob Jones, via DC Comics

Mr. Giordano worked in the comic book industry for more than 40 years. As an editor at DC, he oversaw projects that signaled a new level of maturity in the medium, including “The Dark Knight Returns,” about an aging Batman, and “Watchmen,” about heroes in a world on the brink of nuclear war. During his tenure, DC Comics also introduced its first graphic novel collections, a format that has grown increasingly popular and profitable.