Motion tracking is a well-defined yet application-specific problem of computer vision field, mostly entailing real-time constraints. Methods addressing such problems are expected also to ensure achievements such as high accuracy and robustness. A probabilistic estimation-based approach is proposed in this paper, in order to enhance the real-time motion tracking process of an RGB-Depth device, in terms of accuracy. A novel method is presented for tracking hand-palm of a moving human subject to this end, under a sequence of assumptions such as indoor environment, single object, smooth movement and stable illumination. Tracking accuracy is improved within a particle filter framework by fusing device output with the newly-extracted information from RGB and depth images. Experimental results are shared revealing the advantages of the proposed method over the built-in device algorithms. The results demonstrate that the proposed method produces smaller RMSE values both for single implementations and multi-execution trials without violating real-time constraints.