In this paper, we demonstrate a simple modeling of boron diffusion in Si1-x-yGexCy by manipulating the strain and the intrinsic carl icr concentration. We show that the diffusion of boron is strongly suppressed by a moderate concentration of substitutional C in Si1-xGex. This suppression is due to an under-saturation of Si self-interstitials in the C-rich region. The results obtained from the proposed model are in better agreement with the measured values.