After working as a lawyer, a legal consultant for the Osthilfe government program reducing agricultural debt in East Prussia, and for the municipal government in Breslau, Yorck served on the Reich Price Commission in Berlin from 1936 to 1941 as the department head responsible for fundamental issues. He refused to join the NSDAP and was thus no longer promoted from 1938 on. He first became involved in the resistance in 1938, working in close collaboration with his friends Fritz-Dietlof Graf von der Schulenburg and Ulrich-Wilhelm Graf von Schwerin von Schwanenfeld. After the Kristallnacht pogroms of 9-10 November 1938, he set up a discussion group on the principles of a new Reich constitution.