A series of N4 -aryl-substituted 5-fluoroisatin-3 thiosemicarbazones 3a–3l was synthesized and evaluated for selected biological activities. The brine shrimp lethality bioassay was carried out to study their in vitro cytotoxicity potential and besides, their antifungal, phytotoxic and urease inhibitory effects were also investigated. Seven compounds i.e. 3a, 3d, 3f, 3g, 3h, 3j and 3k proved to be active in the brine shrimp assay, displaying promising cytotoxicity (LD50 = 6.89 9 10-5 –2.79 9 10-4 M). Amongst these, 3a and 3h were found to be the most active ones (LD50 = 6.89 9 10-5 and 9.79 9 10-5 M, respectively). Compounds 3i, 3j and 3 k displayed moderate (40 %) antifungal activity against one or two fungal strains i.e. A. flavus and/or M. canis. In phytotoxicity assay, all the synthesized compounds, including the reference point 2m showed weak-to-moderate (15–70 %) activity at the highest tested concentration (500 lg/mL). In urease inhibition assay, compounds 3f, 3g and 3j proved to be the most potent inhibitors, demonstrating relatively a higher degree of enzymatic inhibition with IC50 values ranging from 37.7 to 47.3 lM.