The influence of polymer chain orientation as well as multi-walled carbon nanotube (MWCNT) alignment on the creep-resistant behavior of nanocomposites has not been fully revealed yet. In this work, tensile and creep behaviors of MWCNT modified polycarbonate nanocomposite fibers produced by melt-spinning at different draw-down ratios have been studied at a temperature of 120 degrees C. For fibers with 2 wt.% MWCNTs, it was found that the Young's modulus and creep resistance show clear dependence on the orientation degree of the polymer chains and the alignment of the nanotubes. Parametric studies based on Burger's model and Weibull distribution function were employed to understand the reinforcing mechanisms. Polarized Raman spectroscopy was utilized to evaluate the orientation degree of nanotubes, and further to reveal the variation in alignment during creep deformation. The results show that Raman analysis was consistent with the creep results. (C) 2013 Elsevier Ltd. All rights reserved.