Polyethylene crystallization under shear has been studied in the presence of single-wall, few-wall, and multiwall carbon nanotubes (SWNT, FWNT, and MWNT). Polyethylene crystal d-spacings for (110) and (200) planes in polyethylene/carbon nanotubes (CNT) are smaller than in the control polyethylene without CNT and the polymer chain is oriented along the CNT axis. The single-wall carbon nanotube templated polyethylene crystals do not redissolve in boiling xylenes; instead, the chain morphology transforms to an amorphous conformation but remains oriented along the nanotube axis. SWNT crystal peaks were also observed in polyethylene/SWNT fibers.