Based on a previous study from our group, fifteen new tetrahydrocarbazoles (THC) incorporating 5-arylidene-4-thiazolinone scaffolds at one position were synthesized and characterized by spectroscopic, elemental and X-ray crystallographic techniques. The new hybrids were evaluated for their anti-proliferative activity against a panel of eight human cancer cell lines utilizing Sulforhodamine B (SRB) assay with doxorubicin as a reference. Among all synthesized THC based hybrids, compounds 11c and 12c revealed the highest potency and selectivity against Jurkat (IC50 1.44 ± 0.09 μM), U937 (IC50 1.77 ± 0.08 μM) and HCT-116 (IC50 6.75 ± 0.08 μM) cell lines, while against normal cell line HME1 (IC50 > 50 μM). To validate the multitarget approach, topoisomerases, tubulin and EGFR inhibition assays were performed. Results indicate that compound 11c inhibited Topo Iα (IC50 52.12 μM), Topo IIα …