One of the most successful-and durable-animation producers of all time, Lantz learned resourcefulness and resiliency early on. His mother died giving birth to his younger brother, and his father was an invalid, so Walter shouldered family responsibilities right from the start. At the age of 15 he got a job as an office boy in the art department of William Randolph Hearst's "New York American" newspaper, and took art courses at night. One year later, his boss recommended him for a job at Hearst's new animation studio. By the age of 18 he was a full-fledged animator, drawing such Hearst characters as Happy Hooligan, Krazy Kat, and the Katzenjammer Kids.

After the Hearst studio closed, Lantz worked for the Barre/Bower Studio, and then signed with John R. Bray, where he became studio manager and developed his own cartoon series, notably "Dinky Doodles," a variation on Max Fleischer's "Out of the Inkwell" series in which Lantz appeared on camera along with his animated stars. In 1927, Bray shut down his studio, and Lantz moved to Hollywood, where he worked for several years as a gagman for Mack Sennett. After a similar stint for Hal Roach, he found himself at Universal, working on the Andy Gump comedies, and came to meet the studio's founder and president, Carl Laemmle, who gave him the opportunity to launch a cartoon department right on the lot.
Lantz inherited the character of Oswald the Lucky Rabbit, whose cartoons had been distributed by Universal up to that point (made first by Walt Disney, and then by a splinter group of Disney animators working for M. J. Winkler). With a formidable schedule of 26 films a year, Lantz took in veteran animator Bill Nolan as his partner to split the directing chores. But first, they completed an unusual assignment: an introductory sequence for Universal's multimillion-dollar musical, The King of Jazz (1930), with Paul Whiteman. Their jaunty musical number featured the voice of Whiteman vocalist Bing Crosby, and was the first animated cartoon to be made in two-color Technicolor.

Lantz's output was steady but unspectacular through the 1930s, though such talents as Tex Avery and Preston Blair were among his animators. In 1935 he and Nolan parted company, and a year later Lantz set up his own production entity with Universal as his distributor. He introduced other characters in the late 1930s, but the first to really catch on was Andy Panda, who debuted in Life Begins for Andy Panda (1939). A year later, Andy was bothered by a grotesque-looking woodpecker in Knock Knock (1940) and Lantz's biggest star was born: Woody Woodpecker. Woody fit right in with the brash, often violent characters of the 1940s, and though his looks, voice, and manner changed over the years, he was Lantz's bread-and-butter for decades to come. Among his best cartoons: The Barber of Seville, Ski for Two (both 1944), Woody the Giant Killer (1947), Termites From Mars (1952). His theme song was even nominated for an Academy Award in 1948. Mel Blanc originally provided Woody's voice; then gagman Ben Hardaway took over, though his speaking voice was sped up for the final effect. In the early 1950s, Walter's wife Grace Stafford assumed the job and was the voice of Woody the rest of her life.

Lantz left Universal briefly in the late 1940s, and suffered financial reverses that caused him to close down for more than a year. In 1950 he re-signed with Universal, and continued producing a regular slate of cartoons for them through 1972, by which time most of his colleagues had given up on theatrical short subjects. Woody remained his leading star to the very end, along with penguin Chilly Willy and, in later years, The Beary Family.
Talented animators and directors passed through Lantz's studio over the years, including Shamus Culhane, Grim Natwick, Dick Lundy, Jack Hannah, and for a brief time in the 1950s, Tex Avery, but it was usually a way station. Lantz's typical output was serviceable but uninspired. He followed Walt Disney's lead and hosted "The Woody Woodpecker Show" on TV in the late 1950s, showing his young viewers how cartoons were made in fascinating weekly installments. He received an honorary Academy Award at the 1979 ceremonies, for "bringing joy and laughter to every part of the world through his unique animated motion pictures."