Abstract: The effect of malaria parasites and chloroquine in mice was examined. The importance of this study derives from the prevalence of malaria in the tropical and subtropical regions, as well as the declining therapeutic efficacy of chloroquine as a first line treatment against malaria infection in these endemic areas. This study aimed to determine the pattern of possible alterations in some haematological and antioxidant molecules in mice treated with either Plasmodium or chloroquine. Three groups of ten mice each categorized as control, non parasitized chloroquine treated (NPcqT) and Parasitized non treated (PnT) were used in this study. Observations from the work show that parasites in mice significantly (p<0.05) increased plasma total protein, globulin, erythrocyte fragility, total bilirubin, oxidative stress, glucose-6-phosphate dehydrogenase (G6PD), liver superoxide dismutase (SOD) and catalase (CAT) enzyme activities. Also the study showed that there is a significant (p>0.05) decrease in plasma SOD, CAT, reduced glutathione (GSH), liver G6PD and GSH. Parasitemia also reduced significantly (p<0.05) mice packed cell volume (PCV). Chloroquine treatment of Non Parasitized (NP) mice increased significantly (p<0.05) erythrocyte fragility, plasma total bilirubin, oxidative stress, but reduced (p<0.05) mice PCV, plasma SOD, CAT, G6PD, GSH but increased (p<0.05) liver SOD, CAT and reduced GSH significantly (p<0.05). The results obtained from the statistical analysis of data suggest that both malaria parasites increase oxidative stress in mice and chloroquine increases SOD and CAT activity in hepatic tissue of mice.