The microstructure and electrical properties of the Pr6O11-based varistor ceramics composed of Pr6O11–Sb2O3 ceramics were investigated in the Sb2O3 content range 0–5.0 mol%. The samples were fabricated by conventional ceramic techniques. The results demonstrated that the addition of Sb2O3 to Pr6O11 can promote the grain growth and the densification of the Pr6O11-based ceramics. The average grain size of Pr6O11 increased and then decreased as the Sb2O3 content increased, reaching 16.4 μm by doping with 1.0 mol%. Highly dense ceramics were obtained, and the relative density reached the maximum value of 96.8%. System densification was attributed to a mass transport mechanism, caused by the presence of Sb2O3, which could favor the oxygen vacancy apparition. Only phase corresponding to Pr6O11 in the sample was detected within the limit of detection of the XRD technique. The electric measurement indicated that the minor incorporation of Sb2O3 can improve the nonlinear electrical properties. This change was ascribed to the Schottky barriers at interface of grain boundary.