Barnett Newman wrote catalogue forewords and reviews and also organized exhibitions before becoming a member of the Uptown Group and having his first solo show at the Betty Parsons Gallery in 1948. Soon after his first exhibition, Newman remarked in one of the Artists' Session at Studio 35: "We are in the process of making the world, to a certain extent, in our own image." Utilizing his writing skills, Newman fought every step of the way to reinforce his newly established image as an artist and to promote his work. An example is his letter on April 9, 1955, "Letter to Sidney Janis: ...it is true that Rothko talks the fighter. He fights, however, to submit to the philistine world. My struggle against bourgeois society has involved the total rejection of it."

Throughout the 1940s he worked in a surrealist vein before developing his mature style. This is characterized by areas of color separated by thin vertical lines, or "zips" as Newman called them. In the first works featuring zips, the color fields are variegated, but later the colors are pure and flat. Newman himself thought that he reached his fully mature style with the Onement series (from 1948). The zips define the spatial structure of the painting, while simultaneously dividing and uniting the composition.

The zip remained a constant feature of Newman's work throughout his life. In some paintings of the 1950s, such as The Wild, which is eight feet tall by one and a half inches wide (2.4 meters by 2 centimeters), the zip is all there is to the work. Newman also made a few sculptures which are essentially three-dimensional zips.

Although Newman's paintings appear to be purely abstract, and many of them were originally untitled, the names he later gave them hinted at specific subjects being addressed, often with a Jewish theme. Two paintings from the early 1950s, for example, are called Adam and Eve (see Adam and Eve), and there is also Uriel (1954) and Abraham (1949), a very dark painting, which as well as being the name of a biblical patriarch, was also the name of Newman's father, who had died in 1947.

The Stations of the Cross series of black and white paintings (1958–66), begun shortly after Newman had recovered from a heart attack, is usually regarded as the peak of his achievement. The series is subtitled "Lema sabachthani" - "why have you forsaken me" - the last words spoken by Jesus on the cross, according to the New Testament. Newman saw these words as having universal significance in his own time. The series has also been seen as a memorial to the victims of the holocaust.

Newman's late works, such as the Who's Afraid of Red, Yellow and Blue series, use vibrant, pure colors, often on very large canvases - Anna's Light (1968), named in memory of his mother who had died in 1965, is his largest work, 28 feet wide by 9 feet tall (8.5 by 2.7 meters). Newman also worked on shaped canvases late in life, with Chartres (1969), for example, being triangular, and returned to sculpture, making a small number of sleek pieces in steel. These later paintings are executed in acrylic paint rather than the oil paint of earlier pieces. Of his sculptures, Broken Obelisk (1963) is the most monumental and best-known, depicting an inverted obelisk whose point balances on the apex of a pyramid.
 
Broken Obelisk in the University of Washington's Red Square
Newman also made a series of lithographs, the 18 Cantos (1963–64) which, according to Newman, are meant to be evocative of music. He also made a small number of etchings.
Newman is generally classified as an abstract expressionist on account of his working in New York City in the 1950s, associating with other artists of the group and developing an abstract style which owed little or nothing to European art. However, his rejection of the expressive brushwork employed by other abstract expressionists such as Clyfford Still and Mark Rothko, and his use of hard-edged areas of flat color, can be seen as a precursor to post painterly abstraction and the minimalist works of artists such as Frank Stella.

Newman was unappreciated as an artist for much of his life, being overlooked in favour of more colorful characters such as Jackson Pollock. The influential critic Clement Greenberg wrote enthusiastically about him, but it was not until the end of his life that he began to be taken really seriously. He was, however, an important influence on many younger painters.