A miniaturised implantable antenna with dual-band operation the Medical Implant Communications Service (MICS) (402–405 MHz) and Industrial, Scientific, and Medical (ISM) (2400.0–2483.5 MHz) bands is presented. The size of the proposed antenna is 31.5 mm³ (8.75 mm × 7.2 mm × 0.5 mm) which is the smallest size compared to previous implantable antennas. A serpentine-shaped radiating patch and open-end slot placed on the ground plane are used for miniaturisation. The performance of the antenna was evaluated from measurements and is based on good agreement with simulations.