We have investigated the influence of ruthenium doping on magnetic and magnetocaloric properties of Pr0.67Ca0.33Mn1 - x RuxO3 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) compounds. X-ray results revealed that the samples have an orthorhombic structure with Pnma space group. The magnetization analysis also showed that Ru doping destroys CO antiferromagnetic and simultaneously inducing ferromagnetism. Variation of lattice parameters and magnetization measurements revealed the existence of mixed valence states of Ru3+ and Ru4+. With increasing Ru content, a slight increase in Curie temperature and magnetization values was observed until x = 0.15. At further Ru doping rates, a considerable decrease was observed in Curie temperature and saturation magnetization. Such a behavior at high Ru concentration rates in saturation magnetization and Curie temperature was attributed to a smaller magnetic moment of Ru4+ than that of Mn3+ and Mn4+ and increase of AFM interaction between the Ru3+- Mn3+ and Ru3+- Mn4+ pairs. The decrease in |Delta S-m| was attributed to the second-order magnetic phase transition and the reduction in saturation magnetization.