Functionalized multi-walled carbon nanotubes (FMWCNTs) have been incorporated into binary composites of poly(amide-imide) (PAI) and polyaniline (PANI) to improve their conductive and mechanical performances. The conductivity of PAI/PANI/FMWCNTs ternary composites significantly increased from 10(-3) to 8.3 S m(-1) with increasing the weight ratio of FMWCNTs from 0 to 10 wt%, which is much higher than that of the sum of PAI/PANI and PAI/FMWCNTs binary composites. The enhanced conductivity is mainly ascribed to be the more intensive conductive percolating network formed in the PAI/PANI/FMWCNTs ternary composites due to the hydrogen bond interaction among PAI, PANI and FMWCNTs. On the other hand, the tensile strength has been improved by 40% from 25 to 35 MPa. The self-extinguishing property and phase transition of the ternary films have also been investigated by thermal gravimetric analysis and differential scanning calorimetry, respectively. It is found that the weight ratio of FMWCNTs and the special morphology are the two important factors that induce such unusual properties. POLYM. ENG. SCI., 59:E224-E230, 2019. (c) 2018 Society of Plastics Engineers