The mechanical properties of novel boron pnictides have been studied by calculating the elastic tensors through finite distortions of the lattice. The resulting elastic constants C ij (where i and j correspond to the lattice directions) are presented in Table . All C ij values of all crb BX are positive, indicating mechanically stable phases. Along the series, there is a clear tendency for the C ij values to decrease due to the increase in atomic radii. As expected, the template (C1) 4 (C2) 4 has the highest C ij values, followed by crb BN. For heavier pnictogens, a significant decrease in the elastic constants is observed, and for Sb and Bi this decrease is particularly pronounced.