Abstract In this paper, we have investigated relaxation mechanisms and dielectric characteristics of an Sr 0.61− x Ba 0.39Nb 2O 6Ce x (abbreviated as SBN61 and x=0.0066) single crystal with dielectric spectroscopy measurements. The crystal undergoes a ferroelectric phase transition at 340 K. The temperature dependence of the real and imaginary part of the complex dielectric susceptibility in the vicinity of ferroelectric–paraelectric phase transition has been studied in the frequency region 100 Hz–10 mHz. The measurement of the dielectric constants of the real and imaginary parts shows strong frequency dependence. The investigations of the dielectric constant using Cole–Cole plots revealed a non-Debye-type dielectric relaxation for Ce +3-doped SBN61. It reveals the coexistence of the two dielectric relaxators in the vicinity of the phase transition.