Tumor progression is accompanied by dysregulation of cell proliferation and apoptosis, which plays an essential role in breast cancer pathogenesis and cell resistance to chemotherapy. The role of protein carbonylation in molecular mechanisms of regulating MCF-7 breast cancer cell proliferation under the effect of roscovitine, a selective inhibitor of cyclin-dependent kinases, was evaluated. The cells were grown in adherent cell culture with or without roscovitine. The levels of reduced/oxidized glutathione and the concentration of protein carbonyl derivatives were determined by spectrophotometry. The cell cycle was evaluated by the flow cytometry; the same technique was used to measure the reactive oxygen species (ROS) concentration. Cell culture with roscovitine resulted in a decrease in the redox potential of the glutathione system and a rise in the ROS and protein carbonyl derivative concentrations. Roscovitine contributed to the G0/G1 and G2/М phase arrest due to its interaction with ATP-binding sites of cyclin-dependent kinases. Roscovitine could also promote enzyme carbonylation. The obtained results can be further used for development of personalized approaches to breast cancer therapy.