Maltin was born in New York City. He began his writing career at age 15, editing and publishing the Film Fan Monthly. After receiving a journalism degree at New York University, Maltin went on to publish articles in a variety of film journals, national newspapers, and magazines, including Variety and TV Guide.

As an author, Maltin is best known for Leonard Maltin's Movie and Video Guide, a compendium of synopses and reviews that first appeared in September 1969 and has been annually updated since October 1987.

He has also written several other works, including Behind the Camera, a study of the art of cinematography, The Whole Film Sourcebook, Leonard Maltin's Movie Encyclopedia, and Of Mice and Magic: A History of American Animated Cartoons.

Since the 1980s, Maltin has had a regular spot on the syndicated television series Entertainment Tonight. He also appears on the Starz cable network and hosted his own syndicated radio program, Leonard Maltin on Video, as well as the syndicated TV show Hot Ticket with Boston film critic Joyce Kulhawik (originally E! personality and game show host Todd Newton).

In the mid-1990s, he became the president of the Los Angeles Film Critics Association and is on the Advisory Board of the Hollywood Entertainment Museum. For nearly a decade, Maltin was also on the faculty of the New School for Social Research in New York City. He currently teaches in the School of Cinema-Television at the University of Southern California.