Using comparative genomic hybridization analysis for an autism spectrum disorder (ASD) patient, a 73-Kb duplication at 19q13.33 (nt. 49562755-49635956) including LIN7B and 5 other genes was detected. We then identified a novel frameshift mutation in LIN7B in another ASD patient. Since LIN7B encodes a scaffold protein essential for neuronal function, we analyzed the role of Lin-7B in the development of cerebral cortex. Acute knockdown of Lin-7B with in utero electroporation caused a delay in neuronal migration during corticogenesis. When Lin-7B was knocked down in cortical neurons in one hemisphere, their axons failed to extend efficiently into the contralateral hemisphere after leaving the corpus callosum. Meanwhile, enhanced expression of Lin-7B had no effects on both cortical neuron migration and axon growth. Notably, silencing of Lin-7B did not affect the proliferation of neuronal progenitors and stem cells. Taken together, Lin-7B was found to play a pivotal role in corticogenesis through the regulation of excitatory neuron migration and interhemispheric axon growth, while further analyses are required to directly link functional defects of Lin-7B to ASD pathophysiology.