A previous study from our laboratory has shown the facilitatory effect of Ceratonia siliqua L. (Fabaceae) on the dopaminergic function. This study investigates the involvement of monoamines in the antidepressant activity of the total polyphenol content of Ceratonia siliqua extract (CS) in mice using a tail suspension test (TST) and forced swim test (FST). The immobility time in the TST and FST were significantly reduced by CS (25 and 50 mg kg(-1), i.p.). The extract considerably attenuated the duration of immobility induced by prazosin (62.5 µg kg(-1), i.p., an α-adrenoceptor antagonist) and eticlopride (0.1 µg kg(-1), i.p., a classical D2-like dopamine receptor antagonist) in both TST and FST, whereas the extract could not modify the immobility in mice treated with p-chlorophenylalanine (100 mg kg(-1), i.p., ×3 days; an inhibitor of serotonin synthesis) and baclofen (10 mg kg(-1), i.p., GABAB agonist). This suggests that the antidepressant effect of CS is mediated by dopamine and noradrenaline.