At some point underground, there are high voltage cables and medium voltage cables that will be crossing each other. Many utilities do not consider or ignore the derating of ampacity caused by multiple cables crossing. In IEC 60287-3-3: Calculation of Power Ratings - Cables Crossing External Heat Sources, the ampacity rating for only two crossing cables is calculated. This paper hence computes the ampacity for multiple cables crossing. Three circuits of high voltage cables crossing three circuits of medium voltage cables were modeled using Computer Simulation Technology (CST) Software. Both the cables were in the parallel configuration with the distance between the circuits and depth of buried varied. Significant temperature rise was found at the point of crossing. If the ampacity were not derated, the temperature exceeds 90°C at the core and becomes unacceptable for the insulation at the point of crossing which causes localized dielectric ageing which may lead to premature cable failures. By extracting the temperature results along the cables at the point of crossing and its vicinity, the localized over-heating at the point of crossing were shown. Also, by adding a steel block between the cables at point of crossing, ampacity can be improved. Hence, this is an important factor that needed to be considered during planning stage.