Banisteriopsis caapi (B. caapi) contains harmine, harmaline, and tetrahydroharmine, has monoamine oxidase inhibitory activity, and has reported antiparkinsonian activity in humans when imbibed as a tea; however, its effects are poorly documented. For this reason, motor function was assessed in 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐treated common marmosets following administration of B. caapi extract (28.4–113.6 mg/kg; po), harmine (0.1 and 0.3 mg/kg; sc), and selegiline (10 mg/kg; sc), alone or with a submaximal dose of L‐3,4‐dihydroxyphenylalanine (L‐DOPA; 4–7 mg/kg). L‐DOPA reversed motor disability, increased locomotor activity, and induced moderate dyskinesia. B. caapi did not increase locomotor activity or induce dyskinesia but at 56.8 and 113.6 mg/kg improved motor disability. The L‐DOPA response was unaltered by co‐administration of B. caapi. Harmine (0.1 and 0.3 mg/kg) produced a mild improvement in motor disability without affecting locomotor activity or dyskinesia but had no effect on the L‐DOPA‐induced antiparkinsonian response. Selegiline (10 mg/kg) alone improved motor function to the same extent as L‐DOPA, but with only mild dyskinesia, and did not alter the response to L‐DOPA, although dyskinesia was reduced. The findings suggest that B. caapi alone has a mild antiparkinsonian effect but does not enhance the L‐DOPA response or reduce dyskinesia.