Two-photon polymerization (2PP) is an effective technique for the fabrication of complex polymeric 3-D micro/nanofeatures and structures using ultrashort pulses from a NIR laser source. The interaction of laser pulses with photoresponsive resin creates a voxel (volumetric pixel) that defines the resolution of the 2PP process. In this work, we present a mathematical model of the 2PP process that considers the effects of radical diffusion and polymerization kinetics on polymerization dynamics. The increase in temperature during the polymerization process and its effect on polymerization kinetics are considered in the model. The developed model is solved numerically to obtain a better understanding of the polymerization dynamics at various time scales. The effects of diffusion and polymerization kinetics on the growth of voxels are analyzed from the presented simulations. A comparison between high and low pulse repetition rate systems is also presented, showing different polymerization dynamics.