We report on the synthesis and on basic superconducting properties of a completely new Mo_2Re_3B ternary boride. The crystal structure of the Mo_2Re_3B compound is characterised by Pmmm space group and the cell parameters: a=11.626 A, b=8.465 A and c=8.026 A. The critical temperature is Tc=8.5 K, whereas the lower and the upper-critical fields at zero temperature are equal to Hc1(0)=19.2 mT and to Hc2(0)=3.7 T, respectively. The corresponding Ginzburg-Landau parameter is equal to k=16.5 and the superconducting gap is estimated to be 2delta/kTc=3.2.