Dodecyl amine-functionalized graphene oxide (DA-GO) was obtained via an amidation reaction. The results of X-ray diffraction and Fourier-transform infrared spectroscopy verified that long alkyl chains of DA were successfully grafted on the GO sheets. Transmission electron microscope and scanning electron microscope techniques illustrated that homogeneously dispersed DA-GO/high-density polyethylene (HDPE) nanocomposites were obtained. The effects of DA-GO on the non-isothermal crystallization of HDPE were then investigated by differential scanning calorimetry (DSC) at various cooling rates (2, 5, 10, and 20 degrees C/min). Significant increase in the onset crystalline temperature (T-o) and the peak crystallization temperature (T-p) of HDPE incorporating DA-GO indicated the strong nucleating ability of DA-GO. The investigation of half-time crystallization time (t(1/2)) demonstrated that crystallization rate of HDPE consisting of DA-GO is faster than that of pure HDPE at a given cooling rate. Ozawa, Avrami, and the combined Avrami-Ozawa methods (Mo) were used for analyzing experimental data. The Mo approach was successful in describing the non-isothermal crystallization process of DA-GO/HDPE nanocomposites. The results indicated that low DA-GO content accelerates the crystallization of HDPE, while higher content hinders the crystallization of HDPE.