Lin28 has been shown to promote proliferation of progenitors and survival of neurons during cortical neurogenesis. However, the role of Lin28 in the terminal maturation of neurons remains obscured. In this study, we investigated the developmental impact of Lin28 overexpression on neurite outgrowth. Lin28 expression was upregulated by in utero electroporation at E14.5. Two days later, electroporated cortices were dissociated for culturing primary cortical neurons. We found that Lin28 overexpression, which was confirmed immunocytochemically, led to neurite underdevelopment for all time points during culture. Specifically, Lin28-overexpressing cells displayed significantly fewer primary neurites and a decreased dendritic branching index, compared to GFP-expressing controls. Additionally, Lin28 overexpression in primary cortical neurons induced the expression of high mobility group AT-Hook 2 (HMGA2). Taken together, our study demonstrates that constitutive Lin28 expression disrupts cortical neurogenesis resulting in impaired neurite outgrowth with a concomitant induction of HMGA2.