Tropical forest understories play a crucial role in maintaining biodiversity and ecosystem dynamics, yet they remain under-explored in ecological studies. This study aims to investigate the diversity patterns and ecological interactions present in the understories of tropical forests in Southeast Asia and Africa. Surveys were conducted across multiple forest sites in Malaysia, Indonesia, and Zambia, employing systematic sampling methods to catalog species composition and density. We utilized multivariate analysis to assess biodiversity indices and ecological interactions, including competition and mutualism among plant species. Our findings reveal a complex web of interactions dominated by shade-tolerant species, with significant variation in species richness and composition across different geographical locations. Results indicate that local climate and soil conditions are primary drivers of these variations. Conclusions drawn from this study highlight the critical role of understory vegetation in forest ecosystem services, such as carbon sequestration and habitat provision, underscoring the need for conservation strategies that prioritize these layers. The research contributes to a deeper understanding of tropical ecology and offers insights into sustainable forest management practices.