The main goal of the study was to determine whether hypoxia augments the toxicity of anticancer drugs towards cardiomyocytes. Drugs selected for this experiment were those that disturb the cardiac redox equilibrium. Cardiomyocytes were incubated for 24 h with doxorubicin, tirapazamine, and 5-fluorouracil, each at three doses, under normoxia and under 50% and 90% hypoxia. The cytotoxic effect was evaluated on the basis of the percentage of living cells, cell vitality (assessed by the MTT assay), and morphology. In addition, the oxidative marker and pH value were determined. Varied protective effects of hypoxia on cell morphology were observed in all cases except the medium concentration of tirapazamine. The 50% hypoxia prevented the toxic effects of all tested drugs. The 90% hypoxia, on the other hand, was effective against the cytotoxic action of doxorubicin and 5-fluoruracil, but the cytotoxicity of tirapazamine increased. It was found that under the 90% hypoxia the oxidative stress observed under normoxia and the 50% hypoxia was greatly reduced. The study revealed that the above drugs did not activate anaerobic glycolysis.