In 1937, at the age of eighteen, McLarty enrolled at the Museum Art School (now the Pacific Northwest College of Art), where his teachers included painter Clara Jane Stephens. He moved to New York City in 1940 and studied at the American Artists School with Sol Wilson, muralist Anton Refregier, and Joe Solman, whose paintings and prints of the urban scene were inspirational to McLarty. For a time, he rented a room from the painter Louis Bunce and his wife Eda, who had Oregon ties.

 Returning to Portland in 1942, McLarty worked in the shipyards, helped his parents operate their hotel, and painted works in response to the Portland urban scene. Printmaking and painting became his primary media. 

In 1946, he married Barbara Lever, a Linfield College graduate who worked at the Portland Art Museum. The next year, he was hired as an instructor at the Museum Art School, where he taught until 1981. His courses included painting, composition, and life drawing, which he emphasized as the basis of all two-dimensional media. His parents’ working-class background had made him aware of social injustice and oppression, and he encouraged his students to understand that art could be a means of commentary and resistance.

McLarty’s paintings and prints are figurative works that relate to Surrealism, German Expressionism, and the work of French artist Georges Rouault and Mexican muralist Diego Rivera. Giant in Trouble (1982), for example, shows a recurring figure in McLarty's art—a bloated giant seemingly bent on destruction, in this case looming over a Portland-like city. His paintings often convey a frightful gaiety. In this painting, the giant is bombarded by an acrobat, whimsical helicopters and airplanes, and animals suggestive of the pottery that the McLartys collected during their trips to Mexico.

Jack and Barbara McLarty established the Image Gallery in their home on Northwest Overton Street in 1961, where they focused on regional contemporary art and native arts of Mexico and Alaska. They operated the gallery in different locations for twenty-five years and sold it in 1986. 

McLarty showed his work at the Image Gallery and in numerous juried and invitational group and one-person exhibitions in Portland, Seattle, and San Francisco. His work appeared in the exhibition Recent Painting USA at the Museum of Modern Art in 1962 and Art of the Pacific Northwest, organized by the Smithsonian in 1974. His work is in the collections of the Portland Art Museum, Seattle Art Museum, Oregon Percent for Art collections, Jordan Schnitzer Museum of Art (University of Oregon), and Hallie Ford Museum of Art (Willamette University), with prints in many other American university collections.

Jack McLarty died on July 10, 2011.