Orphaned at four years of age, Williams was the only African-American student in his elementary school. He studied at the Los Angeles School of Art and Design and at the Los Angeles branch of the New York Beaux-Arts Institute of Design Atelier, subsequently working as a landscape architect. He went on to attend the University of Southern California, designing several residential buildings while still a student there. Williams became a certified architect in 1921, and the first certified African-American architect west of the Mississippi.
He married Della Mae Givens on June 27, 1917, at the First AME Church in Los Angeles. They had three children: Paul Revere Williams, Jr. (born and died June 30, 1925, buried in Evergreen Cemetery, Los Angeles); Marilyn Frances Williams (born December 25, 1926); and Norma Lucille Williams (born September 18, 1928).
Williams won an architectural competition at age 25, and three years later opened his own office. Known as an outstanding draftsman, he perfected the skill of rendering drawings "upside down." This skill was developed because in the 1920s many of his white clients felt uncomfortable sitting directly next to a black man. He learned to draft upside down so that he could sit across the desk from his clients who would see his drafts right-side-up.
Struggling to gain attention, he served on the first Los Angeles City Planning Commission in 1920.
From 1921 through 1924, Williams worked for Los Angeles architect John C. Austin, eventually becoming chief draftsman, before establishing his own office.