Abstract The problem of drug dependence still remains unresolved. In the present study, the effects of water–alcohol extract of Papaver rhoeas on the expression and acquisition of naloxone-induced jumping and diarrhea in morphine-dependent mice were investigated. Administration of three daily doses of morphine (12.5, 25 and 50 mg/kg) for three days in order to develop dependence to morphine caused a significant and dose-dependent increase in the number of jumping and diarrhea when the animals were challenged with naloxone (4 mg/kg). On the other hand, administration with the plant extract (25, 50 and 100 mg/kg) did not show any effect. Injection of extract (25, 50 and 100 mg/kg) 30 min before the naloxone administration in morphine-dependent mice decreased the number of jumping and diarrhea. Administration of extract (25, 50 and 100 mg/kg) 30 min before morphine injection increased the number of jumping but decreased the diarrhea. It could be concluded that the extract of Papaver rhoeas can ameliorate the withdrawal syndrome in morphine-dependent mice. Therefore, the extract might be useful to treatment of withdrawal signs in opioid addicts.