This paper presents the prototype design and development of a miniature MR-compatible fiber optic force sensor suitable for the detection of force during MR-guided cardiac catheterization. The working principle is based on light intensity modulation where a fiber optic cable interrogates a reflective surface at a predefined distance inside a catheter shaft. When a force is applied to the tip of the catheter, a force sensitive structure varies the distance and the orientation of the reflective surface with reference to the optical fiber. The visual feedback from the MRI scanner can be used to determine whether or not the catheter tip is normal or tangential to the tissue surface. In both cases the light is modulated accordingly and the axial or lateral force can be estimated. The sensor exhibits adequate linear response, having a good working range, very good resolution and good sensitivity in both axial and lateral force directions. In addition, the use of low-cost and MR-compatible materials for its development makes the sensor safe for use inside MRI environments.