In the German Revolution of 9 November 1918, Wels was a member of the Berlin Workers' council ("Arbeiter-und Soldatenrat") of the SPD and USPD. He was appointed military commander of the city and consequently had to deal with the occupation of the Stadtschloss by revolutionary forces including violent fights with Freikorps units. Upon the election of Friedrich Ebert as Reich President on 11 February 1919 he acted as presiding officer of the SPD and was formally elected chairman, together with Hermann Müller, on 14 June.