Ecosystems are open spaces in which invasive alien plants repeatedly spread and establish to expand their distribution. This process is closely linked to the formation and maintenance of metapopulations, as well as securing the space necessary for growth, requiring diverse information such as the plant's life history and interactions with surrounding plants. It was observed that Chamaecrista nictitans, an invasive alien plant that has recently become established in Korea, has settled along the eastern coastal areas of Gangwon Special Self-Governing Province and Gyeongsangbuk Province, forming large-scale colonies. This study aimed to evaluate the ecological factors enabling this relatively recent invader to establish a wider distribution range and form larger populations compared to the native species, Chamaecrista nomame. A distribution map of C. nictitans was developed based on field surveys, and 4 m² plots were established at the sites where each species occurred to investigate the vegetation characteristics and assess the habitat conditions. The results indicated that both species occupied similar growth spaces, such as open grasslands. As annual plants, they require viable space for establishment after germination. It was assessed that C. nictitans can be distributed even in spaces where such viable space is not created by other plants during the post-germination establishment phase. C. nictitans was assessed as having a broader ecological niche compared to C. nomame. These characteristics of C. nictitans are considered the reason for its rapid establishment and wide distribution range in the Uljin-gun and Samcheok-si areas. It is presumed that the species initially settled in coastal areas and subsequently spread inland along with sand used for snow removal. It exhibits a tendency for rapid colonization on road edges or bare ground formed by disturbance, suggesting a high potential for spread from the coast to inland areas. However, due to its high light requirements, the potential for spread into forest vegetation interiors is considered low.