Born on 24 November 1906 in Šiauliai.
Died on 01 05 1996 in Kaunas. Buried in Eiguliai Cemetery.
During the First World War he was with his parents in Rostov-on-Don. In 1921-1929 he worked as a railway worker, a clerk for a road foreman, studied at Šiauliai Adult Gymnasium, and after graduating from it in 1929-1943, he studied Russian language and literature at Vytautas Magnus University (until 1930 - Lithuanian University) and Vilnius University, and attended the theatre seminar of Balys Sruoga. He made his debut in the press in 1930, publishing the short story "New Fashion" in the magazine "Vienybė". From 1930 onwards, he published prose works in the publications "Vienybė", "Diena", "Lietuvos aidas", "XX amžius", "Naujoji Romuva", "Židinys", etc. During the Second World War he published short stories about the 1941 deportations. In 1943-1944 he compiled and published 2 books of the almanac "Bells" in Šiauliai. 1946-1951 m. Head of the editorial office of the fiction publishing house. In 1951 he was accused of anti-Soviet activities for several short stories, arrested, sentenced to 25 years and sent to Siberian camps. In 1955 he returned to Lithuania, worked for a while as a Lithuanian language expert at the Kaunas "Žemprojektas" institute, and in 1956-1966 - as a librarian at the Kaunas 13th Secondary School (now St. Matthew's Grammar School). He signed under various names: Audrūnas, Janonis, K. Janonis, Kazys Janonis. After his retirement, he devoted himself to his work as a translator, translating the works of Anton Chekhov, Maxim Gorky, Konstantin Paustovsky and other writers.
In 2012, a memorial plaque to Kazis Jankauskas (sculptor Stasys Žirgulis) was unveiled in front of the house at 8 Seinų Street in Kaunas.