mRNA localization and local translation enable exquisite spatial and temporal control of gene expression, particularly in polarized, elongated cells. These features are especially prominent in radial glial cells (RGCs), which are neural and glial precursors of the developing cerebral cortex and scaffolds for migrating neurons. Yet the mechanisms by which subcellular RGC compartments accomplish their diverse functions are poorly understood. Here, we demonstrate that mRNA localization and local translation of the RhoGAP ARHGAP11A in the basal endfeet of RGCs control their morphology and mediate neuronal positioning. Arhgap11a transcript and protein exhibit conserved localization to RGC basal structures in mice and humans, conferred by the 5' UTR. Proper RGC morphology relies upon active Arhgap11a mRNA transport and localization to the basal endfeet, where ARHGAP11A is locally synthesized. This translation is essential for positioning interneurons at the basement membrane. Thus, local translation spatially and acutely activates Rho signaling in RGCs to compartmentalize neural progenitor functions.