In the present work, we report a combined experiment and theoretical study on high pressure structural stability of Al2Cu type- Mo2B up to ∼40 GPa. Experiments using rotating anode x-ray source indicate that the ground state tetragonal structure of Mo2B (space group I4/mcm) to be stable up to the highest pressure studied. In addition, the experimental results were complemented by first principles density functional calculations within the projector augmented wave method. The calculated structural parameters are in excellent agreement with present experiments as well as previous reports. The estimated bulk modulus using Birch-Murnaghan equation of state from both experiment (302 GPa) and theory (310 GPa) reveals the ultra-incompressible nature of Mo2B. The much higher bulk modulus of this semi boride as compared to elemental Mo is discussed in terms of Mo-Mo bond distance in their crystal structures. The calculated electronic structure of Mo2B shows a strong Fermi surface nesting along P-P direction, which might also trigger lattice instability and is addressed in detail. © 2015 Elsevier B.V.