Terminalia avicennioides Guill. & Perr. (Combretaceae) is used traditionally to treat malaria in Nigeria. To establish its efficacy, methanolic extract of T. avicennioides bark was investigated for antimalarial activity against Plasmodium berghei (NK-65) in mice. Twenty-five mice in five groups were used for this study. Group 1 was uninfected normal control. Twenty mice infected with P. berghei were grouped as untreated negative control (group 2), 5 mg/kg b.w. p.o. artesunate-treated positive control (group 3), and 100 and 200 mg/kg b.w. p.o. T. avicennioides-treated infected mice (groups 4 and 5, respectively). Four-day suppressive effects on P. berghei and hematological and oxidative statuses of the mice were assessed. Suppression of parasitemia by artesunate and methanolic extract of T. avicennioides (at 100 and 200 mg/kg b.w.) after 1 day of treatment was 10, 18, and 11% respectively; at day 5, the level of suppression was 77, 82, and 84% respectively. P. berghei infection decreased hemoglobin, red blood cell, and lymphocyte counts and increased neutrophil count; artesunate and medicinal plant treatment restored these parameters to normal control levels. Also, artesunate and medicinal plant treatment of infected mice significantly (p < 0.05) increased serum and liver superoxide dismutase activities and significantly (p < 0.05) reduced serum malondialdehyde concentration compared to untreated infected mice. The antimalarial effect of T. avicennioides is comparable to that of artesunate. The restoration of oxidative and hematological statuses, to normal values by T. avicennioides, may provide better protection against the malaria severity and complications.