Uncoupling proteins (UCP) act as transporters in the mitochondrial inner membrane, regulating the discharge of the proton gradient generated by the respiratory chain. Within this family, UCP2 emerges as a multifaceted player in the central nervous system, influencing processes like cellular stress, cell proliferation, and neuroprotection. As UCP2 is co-expressed with oxytocin and vasopressin, the well-known social hormones.Our aim was to explore the role of UCP2 in social behaviour comparing wild-type (WT) and UCP2 knockout (KO) rats using social discrimination test. As possible background mechanism, we examined the differences in the vasopressinergic system in the brain using molecular biological methods.We observed a general effect of KO on the body weight without an influence on food intake. The reduced water consumption of KO rats pointed to a potential involvement of the vasopressinergic system, which might impact also the behaviour. During the social discrimination test KO rats exhibited higher mobility in the initial phase, and both groups displayed greater social interest compared to an empty cage. Immunohistochemical staining revealed differences in the axonal course of AVP cells indicating a possible background on target areas of the "social brain".Our results suggest that changes in energy homeostasis in UCP2 KO rats might influence the vasopressinergic system. These molecular changes can contribute to altered water intake as well as increased curiosity. However, more detailed studies are needed to reveal a possible contribution of UCP2 in the fine tuning of social behaviour.