In this study, the effect of erbium oxide (Er2O3) addition on the microstructure, sinterability and mechanical properties of cubic zirconia (c-ZrO2) was investigated. 0-15 wt% Er2O3 and c-ZrO2 powders were mixed by means of colloidal processing and the specimens were sintered at different temperatures for 1 hour. The XRD results showed the existence of cubic crystal structure in all specimens. The lattice parameter of the specimens decreased with increasing Er2O3 addition up to 10 wt% and remained unchanged after this amount. The grain size of the Er2O3 doped c-ZrO2 specimens dropped up to 5 wt% Er2O3 addition and stayed almost unchanged at higher Er2O3 contents. Both hardness and fracture toughness measurements were done using Vickers hardness tester. The fracture toughness values of the undoped, 1, 5, 10 and 15 wt% Er2O3 doped c-ZrO(2)specimens were found to be 1.64 MPam(1/2), 1.77MPam(1/2), 2.06MPam(1/2), 2.57 MPam(1/2) and 2.31 MPam(1/2) respectively.