Modulated electro-hyperthermia (mEHT) is a selective cancer treatment used in human oncology complementing other therapies. During mEHT, a focused electromagnetic field (EMF) is generated within the tumor, by elevated oxidative glycolysis (Warburg effect) and conductivity of the tumor. The EMF induce cell death by thermal and non-thermal effects. Here we investigated an aggressive, therapy resistant triple negative breast cancer (TNBC) model. 4T1/4T07 isografts inoculated orthotopically into female BALB/c mice were treated with mEHT 3-5 times. mEHT induced the upregulation of the stress related Hsp70 and cleaved caspase-3 proteins, resulting in effective inhibition of tumor growth and proliferation.