Continuous monitoring of the tissue temperature surrounding implantable devices could be of great advantage. The degree and duration of the immune activation in response to the implant, which is responsible for signal deterioration, could be inferred from the associated temperature raise and the heating caused by electrical or optogenetical stimulation could be accurately controlled. Within this work, a thin-film platinum RTD embedded in polyimide and a readout system based on the Wheatstone bridge configuration are presented. The RTD offers a sensitivity of 8.5 Ω· °C−1 and a precision of 4.1 Ω. The accuracy of the complete system calibrated for temperatures ranging from 34 to 41 °C lies between the classes A and B defined by the standard IEC 751, which correspond to tolerances of ±0.22 and ±0.48 °C at 37 °C, respectively.