Lymphatic filariasis (LF) remains endemic in Indonesian wetland ecosystems despite long-term mass drug administration (MDA). Environmental modification may alter mosquito community structure and promote the emergence of alternative vector species. A longitudinal entomological survey was conducted in two endemic villages in Banyuasin Regency, South Sumatra. Adult mosquitoes were collected using indoor and outdoor human landing collections and resting collections. Ecological indices, including abundance, dominance, man-hour density (MHD), and man-biting rate (MBR), were calculated. Molecular detection of Brugia malayi was performed using PCR targeting the yACA gene, followed by sequencing confirmation. A total of 1,342 female Culex mosquitoes representing eight species were collected. Culex quinquefasciatus was overwhelmingly dominant (92.4%), particularly in Muara Sugih Village, and exhibited marked endophagic and endophilic behavior. Biting density and MBR were substantially higher in Muara Sugih than in Sedang Village. PCR and sequencing confirmed the presence of B. malayi DNA in Cx. quinquefasciatus. The ecological dominance, indoor feeding behavior, and molecular evidence of B. malayi infection in Cx. quinquefasciatus suggest its potential role as a supplementary vector in modified wetland ecosystems. Integration of ecological surveillance and molecular xenomonitoring is essential to detect residual transmission and support LF elimination in post-MDA settings.