The bioassay guided fractionation of the acetone extract of the fresh leaves of Murraya koenigii resulted in the isolation of three bioactive carbazole alkaloids, mahanimbine (1), murrayanol (2), and mahanine (3), as confirmed from their 1H and 13C NMR spectral data. Compound 2 showed an IC50 of 109 µg/mL against hPGHS-1 and an IC50 of 218 µg/mL against hPGHS-2 in antiinflammatory assays, while compound 1 displayed antioxidant activity at 33.1 µg/mL. All three compounds were mosquitocidal and antimicrobial and exhibited topoisomerase I and II inhibition activities.