Iwieniec was occupied by Nazi Germany between 25 June 1941 to 6 July 1944. In November 1941, the Germans established an enclosed Jewish ghetto in Iwieniec which also received Jews from the surrounding villages. The ghetto was liquidated on 9 June 1942.
On 19 June the Polish Partisan Unit from the AK Stolpce District captured Iwieniec and destroyed the local German garrison. The city was free for a dozen or so hours. In revenge for the defeat, the Germans murdered about 150 inhabitants of Iwieniec, and many others were deported for forced labour.