Carl Adolf von Sydow was born on 10 April 1929 in Lund, Sweden. His father, Carl Wilhelm von Sydow, was an ethnologist and professor of folkloristics at Lund University. His mother, Baroness Maria Margareta Rappe, was a schoolteacher. Von Sydow was of part-German ancestry. A paternal ancestor, David Sydow ("von" or "Von" was added later to the family surname), emigrated from Pomerania to the Kalmar region in 1724. His mother was also of part-Pomeranian descent. Von Sydow was brought up as a Lutheran, but became an agnostic in the 1970s.