Environmental factors, such as adverse life experiences and family/peer influences have a substantial influence on the development of disorders related to alcohol use. In animals, maternal or peer separation/isolation has been used as an environmental intervention that has been shown to alter neurodevelopment and influence drinking behaviors in rodents and primates. In this study, the effects of adult peer isolation on subsequent ethanol intake were investigated in Wistar rats. Because central tachykinin levels have been reported to differ between rats selected for enhanced ethanol preference, neuropeptide [neurokinin A (NKA), substance P (SP)] concentrations were also estimated. Lower levels of ethanol intake, in a two-bottle free-choice model, were observed on the first day of forced ethanol drinking in the single-housed animals. However, overall ethanol consumption was unaffected by peer isolation. Peer isolation significantly lowered SP and NKA levels in the hypothalamus, but this effect was not related to ethanol consumption or body weight. These data indicate that endogenous SP and neurokinin levels are reduced by isolation housing, but this was not associated with alterations in drinking levels using a two-bottle choice procedure.