We have reported temperature and frequency dependence of dielectric behavior of nanocrystalline Zn1-xCoxO (x = 0.0, 0.01, 0.05 and 0.1) samples prepared by gel-combustion method. The synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and LCR-meter, respectively. The XRD analysis reveals that ZnO has a hexagonal (wurtzite) crystal structure. The morphology and size of the nanoparticles (similar to 10-25 nm) were observed by SEM for 5% Co doped ZnO sample. In dielectric properties, complex permittivity (epsilon(star) = epsilon' - j epsilon ''), loss tangent (tan delta) and ac conductivity (sigma(ac)) in the frequency range 75 kHz to 5 MHz were analyzed with temperature range 150-400 degrees C. The experimental results indicate that epsilon', epsilon '', tan delta and sigma(ac) decreases with increase in frequency and temperature. The transition temperature as obtained in dispersion curve of dielectric constant shifts toward higher temperature with increase Co content. (C) 2012 Elsevier Ltd. All rights reserved.