In 2000, a resident population of Texas Seaside Sparrows (Ammodramus maritimus) was identified at Laguna Atascosa National Wildlife Refuge on the lower Texas coast, extending its known breeding distribution farther south than previously described. We studied this breeding population of Texas Seaside Sparrows from April 2012–January 2013 on the Laguna Atascosa National Wildlife Refuge to obtain population density estimates and describe habitat associations. We estimated seasonal density during one year using a distance sampling approach. We described plant community characteristics and estimated percent ground cover. Density estimates of Seaside Sparrows by season were 3.49/ha (CV = 8.27) for spring, 3.59/ha (CV = 18.16) for summer, 4.07/ha (CV = 9.69) for fall, and 1.91/ha (CV = 21.92) for winter. The dominant plant species along the intertidal zone transect where Seaside Sparrows were detected included turtleweed (aka saltwort; Batis maritima), saltgrass (Distichlis spicata), and bushy seaside tansy (aka sea oxeye daisy; Borrichia frutescens). Previous studies indicated cordgrasses (Spartina spp.) to be a dominant plant species strongly associated with Seaside Sparrows and a predictor of nest success. However, cordgrasses were absent from the intertidal zone where Seaside Sparrows were detected during our study. Habitat associations and conservation plans for Seaside Sparrows should be revised to include the plant community found in this study.