A series of 4-alkylaminoaryl phenyl cyclopropyl methanones (6a-6u and 8a-8c) were synthesized from 4-fluorochalcones (3a and 3b) by cyclopropanation of double bond followed by nucleophilic substitution of F with different amines. The compounds were screened for their antitubercular and antimalarial activities against Mycobacterium tuberculosis H37Rv and Plasmodium falciparum 3D7 strains in vitro respectively. Several compounds (6a, 6d-6h, 6p, 6q and 8a-8c) exhibited good in vitro antitubercular activities with MIC values 3.12-12.5μg/mL and preferentially inhibited the growth of P. falciparum in vitro (4a, 4c, 6a-6d, 6f, 6s, 8a and 8c) with IC₅₀ as low as 0.080 and 0.035μg/mL and SI values 4975 and 6948, respectively. Molecular docking studies and in vitro evaluation against FAS-II enzymes using reporter gene assays were carried out to elucidate the mode of action of these molecules. Two compounds 4a and 6g showed significant inhibition at 25μM concentration of the compound.