The research and development department continues searching for effective and definite anticancer medications that would help eradicate cancer. The thiosemicarbazone ligands with indole fragment were utilized to create four new copper(I) complexes. Several spectral examinations and elemental analyses validated the formation of the complexes (1-4). Single crystal X-ray diffraction (XRD) also proved that complex 4 had the expected tetrahedral structure. Complexes 1-4 were assessed for their cytotoxic property on different cell lines such as immortalized human vascular endothelial (EAhy.926), hepatocellular carcinoma (HepG-2), and bladder cancer (T24), and kidney epithelial normal cells extracted from an African green monkey (Vero). The complexes showed reduced toxicity towards healthy Vero cells while being active in cancer cell lines. While the standard cisplatin revealed IC50 values of 26.60 and 49.90 & mu;M, the N-phenyl substituted complex 3 displayed a superior cytotoxic effect with IC50 values of 13.82 and 24.93 & mu;M towards EAhy.926 and HepG-2 cells, respectively.