Mycotoxins, secondary metabolites of molds, are often found in foods of plant and animal origin. Exposure to mycotoxins is a worldwide problem and their adverse effects on human health, including the development of cancer, can vary depending on the duration of exposure and the concentration of the individual mycotoxin. The incidence of ochratoxin A (OTA) and patulin (PAT) in food is extremely high, and OTA and PAT are thought to disrupt cellular redox homeostasis and lead to metabolic reprogramming of cells, which are among the hallmarks of cancer. In this study, the effect of biologically relevant concentrations of OTA and PAT on cellular redox homeostasis and metabolic changes in the human breast cancer cell lines MCF7 (expressing steroid receptors) and SUM159 (without expression of human epidermal growth factor receptor 2, estrogen and progesterone receptors) was investigated. The influence on cellular redox homeostasis is determined by monitoring the formation of reactive oxygen species and by determining the activity of the cellular antioxidant catalase. The metastatic potential of breast cancer cells was determined by studying cell migration. Measurements of oxygen consumption were used to assess the impact on mitochondrial function and efficiency, while mass spectrometry was used to identify the changes in metabolic profile induced by OTA and PAT. The results of this study show that OTA and PAT alter the metabolism of breast cancer cells, indicating the potential role of oxidative stress as a mechanism that may promote tumorigenesis.