Inefficient drug administration into cancer cells is related to the chemoresistance of cancer cells caused by genetic mutations including genes involved in drug transport, enzyme metabolism, and/or DNA damage repair. The objective of the present study was to evaluate the properties of platinum (NP-Pt), graphene oxide (GO), and the nanocomplex of GO functionalized with platinum nanoparticles (GO-NP-Pt) against several genetically, phenotypically, and metabolically different cancer cell lines: Colo205, HT-29, HTC-116, SW480, HepG2, MCF-7, LNCaP, and Hela B. The anticancer effects toward the cancer cell lines were evaluated by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxyanilide salt (XTT) and bromodeoxyuridine (BrdU) assays and measurements of cell apoptosis and morphology deformations. The NP-Pt and GO could effectively be introduced to cancer cells, but more effective delivery was observed after GO-NP-Pt treatment. The delivery of the GO-NP-Pt nanocomplex significantly decreased the viability of Colo 205 and HepG2 cells, but did not increase the cytotoxicity of other investigated cancer cells. The nanocomplex GO-NP-Pt also significantly increased the apoptosis of Colo 205 and HepG2 cancer cells. The obtained results suggest that the nanocomplex GO-NP-Pt is a remarkable nanostructure that can improve the delivery of Pt nanoparticles into cancer cells and has potential anticancer applications