<p>Over the past few decades, MEMS (Microelectromechanical systems) sensor manufacturing technologies have advanced significantly, leading to their integration into intravascular medical devices like catheters and guide wires. Catheters and guidewires embedded with sensors aid physicians in making more accurate medical judgments and enhance the safety of surgical procedures. However, the narrow diameter and specialized usage conditions of catheters and guidewires make sensor packaging extremely difficult. This paper introduces a method for packaging an ultra-miniature sensor in a medical device using a flexible printed circuit board. We detail the packaging process for a fractional flow reserve (FFR) guidewire and assess its performance. This packaging method can also be applied to a variety of ultra-miniature sensors. The electrical performance of the packaged sensor was measured, revealing that the electrical characteristics of the sensor varied by no more than 4%. The sensor was calibrated based on measurements taken under static pressure after packaging. Computational fluid dynamics analysis in a vascular simulation environment and dynamic pressure measurements were conducted for stenosis levels ranging from 50 to 65%, and different FFR values were observed corresponding to varying degrees of stenosis. These results indicated that the packaging method introduced in this paper had minimal impact on the sensor’s performance and ensures stability even under dynamic pressure condition.</p>