Polyamide 6 (PA6), a commercially important semicrystalline polymer, is widely used in engineering plastics, film and fibers [1][2][3][4], which usually causes fires and consequently leads to huge loss of human lives and property, which, to a certain degree, limits the range of applications. We demonstrate a novel strategy to improve the flame-retardant properties of PA6 by using reduced graphene oxide decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite. Graphene, exhibiting outstanding electronic, mechanical [5][6][7][8] and thermal [9,10] properties, is emerging as a rising star in the field of flame-retardant applications due to its endothermic and stable structure [10][11][12][13]. For example, the peak heat release rate (PHRR) of polyvinyl alcohol (PVA) filled with graphene is reduced by 49% [11]. However, in order to achieve fire resistance, the content of graphene used as flame retardant in polymer should be relatively high. Besides, nanocomposites consisting of polymer and clay, such as montmorillonite and kaolinite, are widely used to improve the flame-retardant properties of polymers [14,15]. Halloysite nanotubes (HNTs), one kind of nanoclay, have attracted research attention as fillers for polymer nanocomposites due to their improvement of mechanical [16,17] Abstract. The improvement of flame-retardant properties of polyamide 6 (PA6) was achieved by using reduced graphene oxide decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite as the additive in PA6 matrix. The intimate integration of reduced graphene oxide (rGO) and halloysite nanotubes (HNTs) through a three-step chemical functionalization, enabled the combination of their unique physical and chemical characteristics together. The nanostructure of HNTs-drGO was determined by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). A morphological study revealed that HNTs-d-rGO was dispersed uniformly in PA6 matrix. From the results of cone calorimetry measurements, the fire retardant properties of PA6 were further improved with the addition of HNTs-d-rGO when compared with that of either HNTs, or GO, or a mixture of HNTs and GO (HNTsm-GO) used in PA6 matrix. The results indicate clearly that higher flame-retardant activity of the integrated HNTs-d-rGO nanostructures than that of the simple mixture verifies the importance of the intimate integration between HNTs and rGO, which ascribe to the combination of the stable silica layer created by HNT and the barrier effect of rGO.