Jonas Mendels studied medicine in Amsterdam, where he sat for his medical finals on 12 April 1933. He specialized in internal medicine. As an internist and radiologist, he was affiliated with the Apeldoornse Bos psychiatric institution. Jonas Mendels was married to Hetty van Gelder.
J.H. Coppenhagen, Anafiem Gedoe‘iem. Overleden joodse artsen uit Nederland 1940-1945 (Rotterdam 2000) 116