A flexible implantable PIFA (Planar Inverted F Antenna) antenna for biomedical applications is proposed in this study. The main notability of this design refers to its subtle dimension, flexibility and subordinate thickness that makes it perfectly suitable for implementing inside human or animal tissues. The antenna is aimed to operate in the Industrial, Scientific and Medical (ISM) band (2.4–2.4835 GHz). The thickness of this antenna is only .735 mm, which implies that this antenna is reliable to perform under bent conditions. The antenna offers a compact design with a dimension of 9.48 mm × 7.8 mm × .735 mm (54.348 mm3). Copper and Rogers R03010 are chosen as the patch material and substrate material accordingly. The antenna is encapsulated inside biocompatible material Rogers R03010 for safety concern in skin or muscle tissues. Several types of calculations and performance measurement of this antenna have been done by using CST Microwave studio in both planar and bent conditions by maintaining all the electrical properties of human skin tissue. Finally, Specific Absorption Rate (SAR) and thermal loss are evaluated to comply with the antenna safety issues.