Kaja Kärner was an Estonian artist. She studied at the State Industrial Art School, the Pallas Art School, and the Tartu State Art Institute between 1937 and 1948. After finishing her studies at the Tartu State Art Institute, she worked there as a drawing teacher. She also became a member of the Estonian Artists' Union. She was a member of the Tartu Circle, of which most were arrested in 1949. Although she was not sent to prison camp, she was expelled from the Artists' Union, lost her job as a teacher, and had to work as a label painter at the Trade Administration in Tartu.

After her friends were released from prison, she too could act more freely. She worked as a freelance artist until 1988. As a member of the Tartu Circle, she used an abstract and colourful style. In 1984, she returned to the Artists' Union. Since 1988 until her death in 1998, she worked as a teacher at the Konrad Mägi Studio.