It is generally believed that only the actin cytoskeleton resides in dendritic spines and controls spine morphology and plasticity. Here, we report that microtubules (MTs) are present in spines and that shRNA knockdown of the MT plus-end-binding protein EB3 significantly reduces spine formation. Furthermore, stabilization and inhibition of MTs by low doses of taxol and nocodazole enhance and impair spine formation elicited by BDNF (brain-derived neurotrophic factor), respectively. Therefore, MTs play an important role in the control and regulation of dendritic spine development and plasticity.