Due to their very high levels of flame retardancy, chlorinated and brominated flame retardants had been the most widely used flame retardant additives in plastics industry. However, these flame retardants lead to formation of very toxic volatiles and by-products during fire. Therefore, the recent trend is to replace all of them with non-halogenated flame retardants. In this respect, the use of nanoclays as a synergist flame retardant is becoming more and more important. Thus, the main aim of this work was to investigate the synergistic flame retardant effect of nanoclays with phosphorous compounds in polyamide-6 composites. For this purpose, exfoliated clay nanocomposites of flame retarded/glass fiber reinforced polyamide-6 were prepared by melt compounding. A flame retardant based on phosphorus compounds was used at various levels in glass fiber reinforced polyamide-6 and nanocomposites. Flammability and fire behaviors were evaluated by limiting oxygen index, UL94 and cone calorimeter tests. Substitution of a certain fraction of the flame retardant with nanoclays was found to significantly reduce the peak heat release rate and delay the ignition in cone calorimeter. Moreover, remarkable improvements were obtained in limiting oxygen index along with maintained UL94 ratings.