This research was accomplished to investigate the kinetics of isothermal crystallization of polyethylene oxide (PEO)/silver nanoplate composites. It was obtained that the spherulites increased in size and numbers with time for the composites with various particle loadings. Additionally, the spherulite growth rate of composites decreased with an increase in the crystallization temperature and increased with the addition of nanoplates. The spherulite growth rate was further analyzed by the theory developed by Lauritzen and Hoffman. The product of the lateral surface free energy (sigma) and the end surface free energy (sigma(e)) decreased with an increase in the content of nanoplates. We proposed the possible crystallization mechanisms of these PEO/nanoplate composites according to the change of sigma and sigma(e) with the presence of nanoplates. A controlled experiment showed a minor change in PEO crystallization with the presence of a surfactant C(16)TAB. This implied that the unique size and shape of nanoplates plays a key role on hindering the primary nucleation of PEO and increasing the spherulite growth rate. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1236-1244, 2011