The effect of compressibility on the critical merging distance of two co-rotating shielded vortices is studied using numerical simulations of two dimensional Euler equations. The simulations were carried out using a combination of sixth order compact finite differencing scheme, a tenth order compact filtering scheme and the classical Runge-Kutta scheme. Characteristic non-reflecting boundary conditions were applied on the domain boundaries. The results have revealed that the critical merging distance decreases as the vortex Mach number is increased. Copyright © ETC 2013 - 14th European Turbulence Conference.All rights reserved.