The after-moulding wet fastness of nylon fabrics was investigated in this study. The performance of nylon 6 and nylon 66 was compared by preparing both fabrics under exactly the same conditions. The after-moulding wet fastness of non-metallised acid dyes of different molecular sizes was also compared in this study. Nylon 6 and 66 fabrics were dyed with 3 sets of dyes, namely, NYLOSAN E, NYLOSAN N and NYLOSAN S dyes of different molecular sizes at 105ºC for 10-20 minutes depending on the shade. Then the fabrics were subjected to fixation at 70ºC for 25 minutes. Finished fabrics were then moulded by contour moulding machine at 195ºC for 60s. AATCC wet colourfastness tests were done and the performance of samples was compared.