Objective : To evaluate the in vivo antimalarial activities of ethanolic leaf and stembark extracts of Anthocleista djalonensis used traditionally as malarial remedy in Southern Nigeria in mice infected with Plasmodium berghei berghei. Methods : The ethanolic extracts of the A. djalonensis leaf (1000 - 3000 mg/kg/day) and stembark (220 - 660 mg/kg/day) were screened for blood schizonticidal activity against chloroquine-sensitive P. berghei in mice. The schizonticidal effect during early and established infections was investigated. Results : The A. djalonensis leaf extract (1000 - 3000 mg/kg/day) exhibited a significant antiplasmodial activity both in the 4-day early infection test and in the established infection with a considerable mean survival time, which was incomparable to that of the standard drug, chloroquine (5 mg/kg/day). The stembark extract (220 - 660 mg/kg/day) also demonstrated a promising blood schizontocidal activity in early and established infections. Conclusion : These plant extracts possess considerable antiplasmodial activities, which justify their use in ethnomedicine and can be exploited in malaria therapy.