Painter and printmaker Alexander Brook was born on July 14, 1898, in Brooklyn, New York. A bout with polio at age twelve left the preteen bedridden and to keep him occupied he was given painting lessons. At age sixteen, having recovered, he entered the Art Students League where he studied for three years, also taking courses at the Pratt Institute.

At the ASL he met artist Peggy Bacon, whom he married in 1920. The two lived in London for one year before returning with their daughter, Belinda, to New York, dividing their time between the two artists' colonies of Woodstock and Greenwich Village and giving birth to son Sandy in 1922. Both artists continued their pursuits and working in realm of realism. Of particular interest to Brook was the human figure, and he became interested in the work of French printmaker Jules Pascin, who, at the time, was living and exhibiting in the United States. Pascin's intimate and sometimes humorous depcitions of women in their boudoirs, as well as more mudane but no less intimate works of daily lives of ordinary people, became a source of inspiration for the realist painter and by the late 1920s Brook had gained critical acclaim for his work. As well, he helped to bolster the studio arts in his circle through his work as assistant director of the Whitney Studio Club (1924 - 1927).

Brook earned accolades for his paintings and prints, including the Carnegie Prize at the Carnegie International Art Exhibition in 1939, second only to Pablo Picasso; the Frank G. Logan Prize at the Art Institute of Chicago in 1927; and the Temple Gold Medal at the Pennsylvania Academy of Art in 1931, among others. His images of the daily lives of Depression-era families and individual portraits, as well as soft, unobtrusive nudes and quiet landscapes made him one of the East Coast's more prominent realists in the 1930s. With the rise of Expressionism and its various subgenres, however, Brook's work became less popular and from the early 1950s he worked intermittantly. He divorced Bacon in the early 1940s, and, in 1945, got remarried to painter Gina Knee. Together they relocated to Sag Harbor, Long Island. Brook retired from painting in 1965. 

He died on February 26, 1980.