The mechanical properties and inflammability of polyamide 6 (PA6) nanocomposites incorporated with Montmorillonite organoclay (MMT) modified with thermal stable ionic liquid surfactants were investigated. The compatibility between ionic liquid-treated MMT and PA6 matrix was improved and the intercalation morphology was achieved, which resulted in the increaseof tensile modulus. However, the addition of organo-MMTs alone did not improve the inflammability of the PA6 nanocomposite, because of strong melt-dripping behavior of PA6 matrix. Addition of auxiliary melamine polyphosphate (MPP) intumescent flame retardant to the nanocomposite prevented the melt dripping and enhanced inflammability performance. The enhanced inflammability of PA6/organoclay/MPP nanocomposites was attributed to the synergistic effect between imidazolium or phosphonium organo-MMTs and intumescent flame retardant MPP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40648.