Intermediate progenitor cells constitute a second proliferative cell type in the developing mammalian cerebral cortex. Little is known about the factors that govern the production of intermediate progenitors. Although persistent expression of stabilized beta-catenin was found to delay the maturation of radial glial progenitors into intermediate progenitors, the relationship between beta-catenin signaling and intermediate progenitors remains poorly understood. Using a transgenic reporter mouse for Axin2, a direct target of Wnt/beta-catenin signaling, we observed that beta-catenin signaling is decreased in intermediate progenitor cells relative to radial glial progenitors. Conditional deletion of beta-catenin from mouse cortical neural progenitors increased intermediate progenitor numbers, while conditional expression of stabilized beta-catenin reduced the intermediate progenitor population. Together, these findings provide evidence that beta-catenin signaling in radial progenitors negatively regulates intermediate progenitor cell number during cortical development.