Cornelis Saftleven was born into a family of artists. He learned to paint from his father Herman, along with his brothers Abraham and Herman Saftleven the Younger. He lived for a time in Utrecht with his brother.
After training in Rotterdam, Cornelis likely traveled to Antwerp around 1632. Rubens is known to have added figures in paintings of Saftleven before 1637. When Rubens died in 1640 there were eight Saftlevens in his collection, four of which with figures added by Rubens.
Among his earliest works are portraits and peasant interiors influenced by Adriaen Brouwer. By 1634 Cornelis was in Utrecht, where his brother Herman Saftleven the Younger was living. The brothers began painting stable interiors, a new subject in peasant genre painting. He also made a double-portrait of himself and his brother in the Two Musicians (c. 1633; Academy of Fine Arts Vienna).