Chain scission of polyamide-6 (PA6) takes place readily during high temperature processing. To prevent possible deterioration in its properties, chain extension of PA6 by the use of bis(glycidyloxy)phenylphosphine oxide (BGPPO), a traditional small molecule flame retardant, has been evaluated in the present study. It was found that the melting torque of PA6 modified by 2.5 minutes' mixing with 1.5 wt% BGPPO was about seven times higher than that of unmodified PA6. As a result of the modification, the proportion of amino and carboxyl end-groups of PA6 was greatly decreased. Accordingly, the tensile, flexural and notched Izod impact strength of the chain-extended PA6 were correspondingly increased, the improvement being superior to that produced using a commercial chain extender. The use of BGPPO for this purpose exemplifies its multifunctional characteristics.