Most remaining tropical forests are under some level of chronic human disturbance, which may favor the proliferation of disturbance-adapted native plants, like some species of tropical lianas. These plants may alter forest structure and composition, but little is known about their effect on ecological processes, such as seed rain. We analyzed the early effects of overabundant lianas on the seed rain of animal-dispersed tree species for 1 year. We analyzed the effect of overabundant lianas on seed rain by cutting all lianas in experimental plots of 314.1 m2, establishing 12 paired plots with and without liana cutting in a disturbed Atlantic Forest remnant in Southeastern Brazil. Rarefied tree seed species richness was higher in plots dominated by lianas (10.9 ± 0.2 and 8.3 ± 1.2 for 500 seeds sampled in liana-dominated and liana-cut plots, respectively), but seed abundance was lower (209 ± 138 and 984 ± 421 seeds m−2 in liana-dominated and liana-cut plots, respectively). Pioneer seed abundance (316.0 ± 116.3 seeds m−2) and species density (3.2 ± 0.3 species trap−1) did not differ among treatments. Lianas may eventually increase local seed rain diversity, while suppressing local tree seed rain abundance. Understanding the impact of the dominance of ruderal species in ecological processes that maintain tropical forests communities, such as seed rain, is crucial to guide the directions for conservation and management of degraded remnants.