Pollock was a major figure in the abstract expressionist movement, detaching line from color, redefining the categories of drawing and painting, and finding new means to describe pictorial space.

He was widely known for his technique of pouring or splashing liquid household paint onto a horizontal surface, enabling him to view and paint his canvases from all angles. It was called "action painting", since he used the force of his whole body to paint, often in a frenetic dancing style. This extreme form of abstraction divided the critics: some praised the immediacy of the creation, while others derided the random effects.

He used hardened brushes, sticks, and even basting syringes as paint applicators.

Continuing to evade the viewer's search for figurative elements in his paintings, Pollock abandoned titles and started numbering his works. He said that he wanted viewers to "look passively and try to receive what the painting has to offer and not bring a subject matter or preconceived idea of what they are to be looking for."

Aside from mural painting, Pollock took various jobs to support himself. He spent one summer as a lumberjack, worked as a janitor at a children's school, and cleaned statues for the Emergency Relief Bureau.

As he painted in an old barn-turned-studio, bugs would often come into contact with Pollock's wet canvases and either leave tracks or get stuck. In "Number 31" (1950) in the collection of the Museum of Modern Art, New York, a fly is still intact, stuck in the right-hand corner amid tiny blobs of pink paint.

His method of painting came from his interest in primitive cultures and he was especially fascinated with Native American Navajo sand painters, whose works were created on the ground with sand of various colors let loose from the hand. He described his abstraction as an attempt to evoke the rhythmic energy of nature.

As Pollock's work was gaining widespread attention, he was struggling with alcoholism and depression. His brothers Charles and Sanford encouraged him to seek treatment, including psychoanalysis in 1937. While the therapy was not successful in curing his drinking problem or his depression, he did have several years of sobriety and productive work before succumbing to his inner demons.

In the late 1930s, Pollock filled several notebooks with sketches of Picasso's Guernica.

In 1999, physicist-artist Richard Taylor used computer analysis to show similarities between Pollock's painted patterns and fractals (patterns that recur on multiple size scales) found in natural scenery, reflecting Pollock's own words "I am Nature". His research team labelled Pollock's style Fractal Expressionism.