In our pursuit to discover new anticancer agents, we have synthesized a new series of 2-aryl-1,3-thiazolidin-4-one derivatives carrying a mandelic acid part. Compounds 3a-h and 4a-j have been synthesized with the cyclization of mandelic acid-derived Schiff bases, their structures have been elucidated with spectral methods (H-1-NMR, C-13-NMR, and LC/MS-APCI) and elemental analyzes (C, H, N). Five compounds 3d, 3e, 4e, 4f, and 4g chosen as prototypes were evaluated against the full panel of 58 human tumor cell lines in the National Cancer Institute's in vitro primary cytotoxicity assay (Bethesda, Maryland). Among the tested compound, 3e showed good cytotoxic effects against melanoma cell line UACC-62. Compounds 3d, 4e, 4f, and 4g showed moderate cytotoxic effects, especially against leukemia cell line, RPMI-8226, non-small cell lung cancer cell lines NCI-H23 and HOP-92, central nervous system (CNS) cancer cell lines SF-295 and SNB-75, melanoma cell line UACC-62, and ovarian cancer cell line IGROV1. It is considered that the in vitro test results of selected compounds are promising and an additional mandelic acid moiety to core structure 2-aryl-1,3-thiazolidin-4-one and different modifications may result in effective agents in anticancer treatment.