This study investigates the regeneration and spread of the invasive alien tree species Acer negundo L. in forest and roadside habitats subjected to different levels of anthropogenic disturbance in Lithuania. A. negundo is considered one of the most aggressive non-native woody species in riparian and disturbed forest ecosystems, posing ecological and management challenges due to its high regenerative capacity. Field investigations were conducted in 2024-2025 in the Dubrava and Jonava regional divisions of the State Forest Enterprise (VMU). Regeneration patterns were assessed in forest sample plots and roadside transects representing recently cut stands, forest edges, and open roadside habitats subjected to repeated mechanical disturbance. Naturally regenerated individuals were classified by height and origin, distinguishing vegetative regeneration associated with stumps and underground woody structures from seed-origin saplings. Additional laboratory experiments were carried out to assess seed germination following cold stratification. The results showed that regeneration was strongly concentrated in disturbed habitats. After cutting, vegetative regeneration clearly dominated: stump-origin shoots accounted for approximately 60% of all regenerants, while other vegetatively regenerated individuals comprised about 30%. Total densities exceeded 38,000 saplings per hectare in roadside transects. Seed-origin individuals represented only about 10% of regeneration in forest stands, indicating limited natural establishment despite the species’ high reproductive potential. Laboratory germination reached 82% after cold stratification, and individual female trees produced on average about 21,000 samaras (42,000 seeds) per season. These findings demonstrate that the persistence and spread of Acer negundo are primarily driven by vegetative regeneration following mechanical disturbance, while seed-based reproduction facilitates longer-distance dispersal and population expansion. The study provides quantitative evidence of the species’ high phenotypic plasticity and explains its invasive success in disturbed forest-edge and roadside habitats of the temperate zone.