A completely new approach for the fabrication of 3-axis thermal accelerometers is presented in this paper. Micromolded polystyrene micro-parts are assembled with polyimide membranes enabling the construction of thermal accelerometers. The use of polymers (polystyrene and polyimide) with low thermal conductivities improves the overall power consumption of the thermal accelerometer and enables a simple and low-cost fabrication process (no clean room infrastructure required). The accelerometer is composed of 4 polystyrene microinjected structural microparts (two identical top parts and two identical central parts) and three polyimide membranes (two identical z-axis membranes and a central membrane). The microinjected parts provide the mechanical support for the active elements that are placed on the membranes (the heater and the temperature sensors). Coupled 3D thermo-electric-fluidic FEM simulations show that current design has a sensitivity of 1.6ºC/g in the X-Y directions and 0.2ºC/g in the Z direction for a central heater temperature of 300ºC. ; Fundação para a Ciência e a Tecnologia (FCT)