The localization of certain mRNAs to dendrites and their local translation in synaptic regions are proposed to be involved in certain aspects of synaptic plasticity. A cis -acting element within the 3′ untranslated region (3′ UTR) of the targeted mRNAs, which is bound by a trans-acting RNA-binding protein, controls the dendritic mRNA localization. Here, we identified hematopoietic zinc finger (Hzf) as a trans-acting factor that regulates the dendritic mRNA localization of the type 1 inositol 1,4,5-trisphosphate receptor (IP 3 RI), a dendritically localized mRNA in cerebellar Purkinje cells, via binding to the 3′ UTR. In Hzf -deficient mice, the dendritic localization of IP 3 RI mRNA and brain-derived neurotrophic factor-induced IP 3 RI protein synthesis in the cerebellum were impaired. These findings suggest that Hzf is an RNA-binding protein that controls the dendritic mRNA localization and activity-dependent translation of IP 3 RI, and may be involved in some aspects of synaptic plasticity.