Sonia Alice Gechtoff was born in Philadelphia, Pennsylvania on September 25, 1926 to Ethel Etya and Russian painter Leonid Gechtoff. Her mother managed art galleries, including her own East West gallery in San Francisco, California. Her father was a highly successful artist from Odessa in the Ukraine who went on to work as an Abstract Expressionist and Futurist. He introduced his daughter to painting at age five and "had [her] sit beside him at his easel with a brush and paints and beginning at age six he was there to spur [her] on."

Gechtoff's talent was recognized early and she was put in a succession of schools and classes for artistically gifted children. She graduated from the Philadelphia Museum School of Industrial Art with a BFA in 1950. Her work at this point was a social realism, influenced by Ben Shahn and the artists of the Young Communist League.

In 1951, she relocated to San Francisco where she enrolled in the California School of Fine Arts, sharing her social and professional life with such famous Bay Area artists as Hassel Smith, Philip Roeber, Madeline Dimond, Byron McClintock and Deborah Remington and Ernest Briggs. She began working with gestural abstraction, influenced by Clyfford Still. According to Gechtoff, female abstract expressionists in San Francisco (such as Jay DeFeo, Joan Brown, Deborah Remington and Lilly Fenichel) did not face the same discrimination as their New York counterparts. At the CSFA she studied lithography with James Budd Dixon.

Gechtoff married fellow Philadelphia-born James Kelly, another noted Bay Area artist whom she met in San Francisco in 1953. Sonia gained national recognition in 1954, when her work was exhibited in the Guggenheim Museum’s Younger American Painters show alongside Willem de Kooning, Franz Kline, Robert Motherwell and Jackson Pollock. Gechtoff’s mother, Ethel, moved to San Francisco in 1955 and opened the famous East-West Gallery, where she exhibited to works of many of the AbEx artists, including the young artists Bruce Conner, Jay De Feo and Roy de Forest.

In 1958, Gechtoff and Kelly moved to New York where she immediately became a part of its art world. She was represented by major galleries, among which were Poindexter and Gruenebaum, receiving consistently excellent reviews for her work. She held teaching appointments and visiting professorships at New York University, Adelphi University, Art Institute of Chicago and the National Academy.

Later in her career, Gechtoff began drawing inspiration from the Brooklyn Bridge, classical architecture, and the sea, whose forms are recognizable in her later collage-like paintings. She was one of eighteen artists featured in Bella Pacifica: Bay Area Abstraction 1946-1963, a Symphony in Four Parts, a 2011 exhibition at four galleries in New York. She was also one of twelve artists included in Women of Abstract Expressionism, an exhibition organized by the Denver Art Museum in 2016 that later toured.

Sonia Gechtoff died on 1 February 2018 in the Bronx, New York.