Effect of isovalent Zr dopant on the colossal permittivity (CP) properties was investigated in (Zr + Nb) co-doped rutile TiO2 ceramics, i.e., Nb0.5%ZrxTi1-xO2. Compared with those of single Nb-doped TiO2, the CP properties of co-doped samples showed better frequency-stability with lower dielectric losses. Especially, a CP up to 6.4 x 10(4) and a relatively low dielectric loss (0.029) of x = 2% sample were obtained at 1 kHz and room temperature. Moreover, both dielectric permittivity and loss were nearly independent of direct current bias, and measuring temperature from room temperature to around 100 degrees C. Based on X-ray photoelectron spectroscopy, the formation of oxygen vacancies was suppressed due to the incorporation of Zrions. Furthermore, it induced the enhancement of the conduction activation energy according to the impedance spectroscopy. The results will provide a new routine to achieve a low dielectric loss in the CP materials.