Isotactic　polypropylene　(iPP)　composites　with　unmodified　and　modified　tetra-needle-shaped　zinc　oxide　whisker　(T-ZnOw)　were　prepared　via　melt　blending　in　a　twin-screw　extruder.　The　mechanical　properties,　thermal　properties,　morphology　and　crystallization　behavior　were　investigated.　The　mechanical　properties　of　iPP　with　T-ZnOw　modified　by　silane　based　coupling　agent　were　much　better　than　that　of　iPP　with　unmodified　T-ZnOw.　The　reason　was　that　the　interfacial　interaction　between　T-ZnOw　and　iPP　matrix　became　stronger　when　T-ZnOw　was　modified　by　coupling　agent.　Besides,　the　addition　of　T-ZnOw　improved　thermal　properties　of　iPP,　including　heat　deflection　temperature　and　thermal　degradation　temperature.　Furthermore,　wide　angle　X-ray　diffraction　(WAXD)　results　showed　that　T-ZnOw　can　be　used　as　a　novel　β-nucleating　agent,　and　the　relative　content　of　β-crystal　was　0.38　when　T-ZnOw　content　was　5.　wt.%.　iPP/T-ZnOw　composites　were　found　to　exhibit　higher　crystallization　temperature,　smaller　spherulites,　and　faster　crystallization　rate　than　those　of　pure　iPP,　indicating　that　T-ZnOw　played　a　role　of　nucleating　agent　on　the　crystallization　of　iPP　and　could　induce　accelerated　crystallization.　©　2011　Elsevier　Ltd.