A catheter for contact force sensing includes a catheter body, a deflectable section, and a distal section having a tip electrode and a contact force sensor for sensing a 3D contact force vector applied to the tip electrode. The contact force sensor has a body and at least one sensor with an electrical characteristic responsive to deformation of the body resulting from the force vector. The sensor receives an electrical current and outputs an electrical signal indicative of a change in the electrical characteristic. The sensor may be a strain gage responsive to tension and compression of at least a portion of the body of the force sensor, and the electrical characteristic may be electrical resistivity of the strain gage. Alternatively, the sensor may be responsive to strain and stress of at least a portion of the body, and the electrical characteristic is inductance or hysteresis loss.