Polarized， non-overlapping， regularly spaced， tiled organization of radial glial cells (RGCs) serves as a framework to generate and organize cortical neuronal columns， layers， and circuitry. Here， we show that mediator of cell motility 1 (Memo1) is a critical determinant of radial glial tiling during neocortical development. Memo1 deletion or knockdown leads to hyperbranching of RGC basal processes and disrupted RGC tiling， resulting in aberrant radial unit assembly and neuronal layering. Memo1 regulates microtubule (MT) stability necessary for RGC tiling. Memo1 deficiency leads to disrupted MT minus-end CAMSAP2 distribution， initiation of aberrant MT branching， and altered polarized trafficking of key basal domain proteins such as GPR56， and thus aberrant RGC tiling. These findings identify Memo1 as a mediator of RGC scaffold tiling， necessary to generate and organize neurons into functional ensembles in the developing cerebral cortex.