Plastic electronics is attracting increasing attention for both high‐end applications such as flexible OLED displays in mobile phones and low‐cost items such as plastic RFID tags for product labelling and tracking. However, there are numerous technological challenges, not the least of which is to develop robust and reliable packaging methods. Unfortunately, most of the established packaging technologies used in conventional silicon electronics are not transferable to plastic electronics due to the high process temperatures involved. We have explored the use of room temperature ultrasonic welding for the realization of multilayer plastic electronic circuits, identifying two distinct modes of ultrasonic welding that can form combined electrical and mechanical connections between adjacent low‐temperature polymer films with either aluminum or printed silver metallisation. We have fabricated fully functional multilayer wireless charging coils and RFID tags to demonstrate the potential of this new system integration approach.