A lyophilized ethanolic aqueous extract of Papaver rhoeas petals was evaluated for its behavioral and pharmaco-toxicological effects in mice and its chemical composition was studied using thin layer chromatography (TLC). In this study, chemical analysis by TLC showed that the petals contain some anthocyanins, whereas no alkaloids were detected. The toxicological effect of alcoholic and aqueous plant extract administered intraperitoneally was determined in mice. The toxicological results obtained indicated that 2000 mg/kg is LD10 and 4000 mg/kg is LD50. Behavioral and pharmacological studies of ethanolic and aqueous extract showed that the plant extract reduced locomotory, exploratory and postural behavior of mice. This was evaluated through two specific behavioral tests; a non-familiar environment test (the Staircase test) and a familiar environment test (Free exploratory test). These behavioral and pharmacological effects are more pronounced when the solvent used for extraction is 10% ethanol and is not antagonized by benzodiazepines, opioids, dopaminergic and cholinergic compounds (flumazenil, naloxone, sulpuride and atropine). The plant extract did not induce sleep in mice after treatment with an infrahypnotic dose of pentobarbital. This finding shows that the plant extract has a sedative effect at a 400 mg/kg dosage.