Early life adversity, such as social isolation, causes a variety of changes to the development of cognitive abilities and the nervous system. Increasing evidence has shown that epigenetic modifications mediate gene-environment interactions throughout the lifespan. In this study, we investigated the effect of adolescent social isolation on cognitive behaviours and epigenetic alterations of the brain-derived neurotrophic factor (BDNF) gene. Male Sprague Dawley rats were randomly assigned to either groupreared or isolation-reared conditions during post-natal days (PNDs) 21–34. On PND 56, all rats underwent behavioural testing and were then sacrificed for biochemical testing. Adolescent social isolation induced impaired PPI. Regarding BDNF, the isolation-reared rats demonstrated increased BDNF mRNA levels, H3 acetylation at the BDNF gene and BDNF protein expression in the medial prefrontal cortex (mPFC). In contrast, the BDNF mRNA levels, H3 acetylation of the BDNF gene and BDNF protein expression were decreased in the hippocampus of the isolation-reared rats. The present study indicated that epigenetic regulation of BDNF may be one of the molecular mechanisms that mediated the cognitive dysfunction. Moreover, the interaction between the mPFC and hippocampus might play an important role in the regulation of cognitive behaviour.