A new family of quinolinone derivatives has been synthesized and evaluated for their antikinetoplastid activities against Leishmania donovani and Trypanosoma brucei brucei. Results from these structure-activity relationship studies enabled identification of compounds 3a and 4g as the most active compounds against L. donovani promastigotes and amastigotes parasites (IC(50) values in a range of 2-11 μM). Additionally, compound 3b has emerged from this study as the most active compound in the series against T. b. brucei with a MEC value of 12 μM. These three compounds are worth of further in vivo evaluation.