At the beginning of the war in September 1939, the Corps, under the leadership of General Werner Kienitz, was assigned to the 14th Army in south Poland with the 44th and 45th Infantry Division. Together with the VIII Army Corps, XVII corps advanced from the Teschen area to the north of the Vistula via Pszczyna to Krakow. It then participated in the successful attack of the XVIII Corps on Lviv under General Eugen Beyer, which concluded the campaign.