Ethnopharmacological relevance: Cymbopogon citratus (DC.) Stapf (Poaceae) is a medicinal plant known for its antimalarial, antipyretic and antifatigue activities in Cameroonian folk medicine. Aim of the study: The aim of this work was to evaluate the prophylactic antimalarial effects of the decoction prepared from the leaves of Cymbopogon citratus on Plasmodium berghei ANKA infection in mice and investigate its action on haematological and serum biochemical status. Materials and methods: Swiss mice were treated with Cymbopogon citratus leaf decoction (25, 50, 100 and 200 mg/kg) and later inoculated with Plasmodium berghei ANKA. The prophylactic antimalarial activity of the decoction was evaluated by determining the parasitaemia, percentage chemosuppression, body weight, body temperature, food and water intake in pretreated parasitised mice. The possible ameliorative effects of the decoction on malaria associated haematological and serum biochemical changes were also assessed. Results: The decoction exhibited a prophylactic activity of 85.32% and its chemotherapeutic effects ranged from 56.88 – 85.32% with maximum effect observed at the highest experimental dose. It significantly inhibited parasitaemia (P < 0.001) compared to the negative control group. Interestingly, treatment of parasitised mice with the decoction significantly restored the malaria modified haematological and biochemical status compared with distilled water-treated parasitised mice. Conclusion: The results of this prophylactic assay indicated that Cymbopogon citratus decoction has antimalarial effects and normalised haematological and serum biochemical aberrations generated by malaria. Hence, Cymbopogon citratus represents a promising source of new antimalarial agents.