The genus Mosla (Lamiaceae) is a small but taxonomically challenging group distributed across East Asia to northern and central Malesia. Despite its morphological plasticity and controversial infrageneric classification, molecular phylogenetic studies have consistently supported its monophyly. To resolve its evolutionary history and clarify species boundaries, we performed whole-genome resequencing of 33 samples representing 12 Mosla species, reconstructed phylogenies using 952 single-copy nuclear genes and plastid datasets, estimated divergence times, and conducted ancestral range and morphological trait reconstructions. Our results strongly support the division of Mosla into two sections (Orthodon and Mosla), with divergence dated to the Middle Miocene (∼17.42 Ma). Biogeographic analyses suggest an ancestral range in southern China, followed by vicariance driven by the opening of the Sea of Japan. Morphological evolution shows rapid diversification in vegetative traits, whereas reproductive structures (e.g., bract and calyx characters) remain phylogenetically conserved. This study provides a robust genomic framework for Mosla taxonomy, elucidates its biogeographic history, and highlights the role of Miocene tectonoclimatic events in shaping its diversification.