The biodegradable poly(butylene succinate) (PBS)/poly(ethylene oxide)-polyhedral oligomeric silsesquioxane (PEO-POSS) nanocomposites were prepared by the solution blending and melt-injection methods. The effect of PEO-POSS on the non-isothermal and isothermal crystallization, morphology, as well as mechanical properties of PBS was carefully investigated. The PEO-POSS nanoparticles dispersed well in the PBS matrix, with the diameters around 30 nm. From isothermal crystallization analysis, the incorporation of PEO-POSS enhanced the crystallization of PBS due to the heterogeneous nucleation effect while the crystal structure of PBS remained. PBS/PEO-POSS nanocomposites showed of higher glass transition temperatures than that of neat PBS, attributing to the existence of PEO-POSS decreasing the flexibility of PBS chains. The elongation at break of the PBS/PEO-POSS nanocomposites reached the maximum value with PEO-POSS content of 5 wt%. However, the elastic modulus of PBS decreased after the incorporation of PEO-POSS. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers