<p>Butterflies are widely regarded as sensitive indicators of ecosystem health, so their declining populations in urban areas are a cause for concern. This study documented butterfly species and butterfly–plant associations across five green spaces in the Bangkok Metropolitan Region, Thailand (Bang Kachao, Bang Ramat, Benjakitti Park, Phutthamonthon Park, and Suan Rot Fai Park). Butterfly observations were collected opportunistically along public walking paths from 2020–2025, primarily included larvae and adults. The butterfly species and their associated host plants were recorded. Because sampling intensity was uneven among sites, pooled data were used to describe the regional butterfly–plant community. Bipartite interaction networks were constructed for pooled data that included: a network with combined adults and larvae, an adult butterfly-plant network, and a larval butterfly-plant network. Across all sites, 83 butterfly species from five families were recorded from 484 observations on 50 plant species and 23 plant families. When analyzing the networks by life stage, the adult network exhibited 2.5 times more unique interaction links, with 1.7 times more butterfly species and 1.6 times more host plant species included. In contrast, the larval network showed 1.5 times higher specialization compared to the adult network, indicating a rigid dependency on specific host taxa during the larval stage. These results serve as a baseline for comprehending the structure of butterfly-plant interactions within the Bangkok Metropolitan Region. They also offer valuable insights into the urban management implications for urban planning and the design of biodiversity-friendly green infrastructure, which can enhance ecosystem functions and services in tropical cities.</p>