For thermoplastic material extrusion 3D-printing functional filaments with electrically conductive, piezoresistive, piezoelectric, capacitive or magnetic properties are developed. The functional filaments result in piezoresisitve static/quasi-static sensors; however, these 3D-printed sensors are manufactured in several processes, for example, the creation of highly conductive paths using embedded copper wires or by silver inking. The multi-process 3D printing of sensors presents an obstacle to smart functional 3D-printed structures where the sensory element is in situ printed at the location and orientation of use, including the electrical paths. This research introduces a three axial piezoresistive accelerometer where the whole sensor, including highly conductive electrical paths, is printed in the same process of thermoplastic material extrusion. The structural components of the sensor are printed with a non-conductive polylactide material, the sensory element with a conductive material that has a relatively high resistivity, and the electrical paths with a conductive material that has a relatively low resistivity. As discussed in the manuscript with single-process sensors, the functional tuning of sensors is as easy as changing the design. The design and manufacturing solutions researched for the triaxial accelerometer can be applied to other 3D-printed sensors, for example, force sensors and opens up the possibility of a single-process 3D-printed smart structure.