Preparation and characterization of nanodiamond dispersed polyamide-based filament were investigated. The nanocomposite filaments exhibited enhanced thermomechanical properties. Transmission electron microscopy (TEM) images showed the ND particles were uniformly distributed in PA matrix, resulting in uniform stress distribution and transfer of applied stress from matrix to reinforcement. This structure lead to the enhancement of tensile strength and toughness of nanocomposite filaments. Furthermore, incorporation of ND into the PA matrix resulted in higher thermal stability, by delaying the thermal degradation of the PA matrix. This composite has a potential for high performance application.