Mathematical modeling of multi-phase Stirling engine systems is presented in this paper. A detailed modal analysis is discussed for a symmetric three-phase system based on the corresponding linearization. This analysis proves the self-starting potential of multiphase Stirling engine systems relying on the theory of nonlinear systems. The start-up temperature of a three-phase Stirling engine example system is derived based on the same modal analysis. The operation of a low-temperature three-phase Stirling engine prototype is discussed based on the developed theory and the internal dissipation of the engine chambers. This discussion reveals the signiflcance of the gas spring hysteresis phenomenon in low-power Stirling engine designs. Further analysis shows that the gas hysteresis dissipation is reduced drastically by increasing the number of phases in a multi-phase Stirling engine system. It is shown that for an even number of phases, half of the engine chambers can be eliminated by utilizing a reversing mechanism within the multi-phase system. The mathematical formulation and modal analysis of multi-phase Stirling engine system is then extended to a system that incorporates a reverser. By introducing a reverser to the fabricated prototype, the experimental system successfully self-starts and operates in engine mode. The system thus proves its self-starting capability and validates the technique for computation of start-up temperature.