The adhesion molecule L1 is expressed in primary melanomas and cutaneous metastases in contrast to melanocytic nevi and melanocytes, and is significantly associated with metastatic spread. Recent studies have demonstrated that in carcinomas L1 expression is associated with sustained activation of the extracellular signal-regulated kinase (ERK) pathway and upregulation of ERK-dependent, motility- and invasion-associated gene products including αvβ3 integrin. The objective of this study was to further investigate the role of the adhesion molecule L1 in melanoma progression, and to evaluate whether targeting the L1 adhesion molecule would have therapeutic effects against invasive melanoma growth. Using human melanoma cells from different stages of progression in monolayer and organotypic human skin culture mimicking the pathophysiological environment of cutaneous melanoma, we found that (1) L1 expression mostly correlates with melanoma progression and αvβ3 integrin expression, (2) overexpression of L1 in early radial growth phase melanoma cells promotes conversion from radial to vertical growth phase melanoma without upregulation of αvβ3 integrin expression, and (3) suppression of L1 function significantly reduces migration and invasion of melanoma cells, but does not completely block invasive melanoma growth. Altogether, L1 plays a critical role in melanoma invasion and progression and offers therapeutic potential in combination with conventional anticancer agents.