Being the basic building blocks of chromatin, nucleosomes and their stability determine the genome accessibility for different DNA-dependent proteins. This characteristic is labile under cell-life processes. One of the abundant DNA-binding proteins, which is important for genome compaction, is poly(ADP-ribose) polymerase1 (PARP1). Despite the extensive experimental data on the chromatin compaction regulation under ADP-ribosylation, the details of the interplay of nucleosome with PARP1 in the absence of protein activation remain unclear. In this study, we discovered unusual changes of the nucleosome wrapping strength upon PARP1 interaction using a single-molecule approach—optical tweezers. We demonstrated that PARP1 binding leads to weakening of the contacts of inner DNA turn in nucleosome.