Structural stability and phase transitions in mixed rare earth sesquioxides (Eu1−xHox)2O3 crystallizing in the cubic bixbyite structure were investigated under high pressure using angle dispersive X-ray diffraction technique. Studies on various compositions of the mixed oxide show that when the average cationic radius, RRE (where, RRE = xRHo+(1−x)REu) is equivalent to or below 0.9164 Å, the system undergoes a cubic to monoclinic transition as a function of pressure, whereas, when RRE equivalent to or above 0.9220 Å it is observed to prefer a transition from cubic to hexagonal structure. Based on our detailed investigations, a pressure-concentration (P−x) phase diagram for (Eu1−xHox)2O3 up to a pressure of 15 GPa is constructed. The bulk moduli for the parent and high pressure phases are calculated from the Birch-Murnaghan equation of state fit to the experimental pressure volume data and are reported. Structural analysis based on refinement has revealed that, an increasing structural rigidity of the cubic phase with decreasing RRE leads to an increase in the transition pressure and bulk moduli except for 0.4 ≤ x ≤ 0.6. The observed significant reduction in bulk moduli and transition pressure for 0.4 ≤ x ≤ 0.6 is due to the increased micro strain/internal pressure developed upon doping.