Phytochemical and biological evaluation of the stem bark of Alysicarpus ovalifolius led to the isolation of three carbazole alkaloids identified as mohanimbine (1), koenimbine (2) and koenidine (3) along with quercetin 3-O-glucoside (4), kaempferol 7-O-glucoside (5), orientin (6), apigenin (7), quercetin (8), plumbagin (9) and stigmasterol (10). The structures of these compounds were elucidated using physical and spectroscopic methods as well as comparison with the literature data. Compound 3 showed strong activity against chloroquine-sensitive strain I (D6) and the multi-drug resistant Indochicha I (W2) of Plasmodium falciparum with IC50 values of 63.07 ± 0.01 and 54.19 ± 0.04 ng/mL, respectively. Compound 1 on the other hand exhibited moderate larvicidal against Anopheles gambiae larvae as well as antimicrobial activities against Candida albicans and gram-positive Staphylococcus aureus, respectively.