Rapid growth in wireless communications has triggered the advent of 5G mobile communication systems. The use of millimeter waves (30-300 GHz) in 5G system has generated global concern about its biological safety. In present paper, we have numerically analyzed the heat transfer in a 3D multilayered skin tissue exposed to 5G frequencies. The numerical scheme comprises coupling of solution of Maxwell's equation of wave propagation within tissue to Pennes’ bioheat equation. Temperature variations are analyzed at 28 GHz, 38 GHz, and 60 GHz. Additionally, electric field and specific absorption rate distribution are also studied. Highest values of electric field and specific absorption rateare estimated in epidermis layer of skin tissue. For all considered frequencies, highest transient temperature (37.36°C) is predicted in subcutaneous fat layer of the skin. However, the steady state temperature is nearly same as core body temperature (37°C). The results show that 5G mobile phones do not cause any thermal damage to the skin tissue and can be considered safe.