This study deals with the comparison of spider diversity and composition in a complex landscape of the Terai Conservation Area (TCA) characterized by alluvial floodplains of tall grassland interspersed with woodland, swamps, and riparian patches. High water table, annual flooding, and annual grassland fire maintain its dynamic complexity. A mosaic of five vegetation types was sampled for spiders from March 2005 to August 2006 by using pitfall traps and other semi-quantitative collection methods along transects. A total of 3666 adult spiders representing 22 families, 60 genera, and 160 species were found. Using the abundance-based estimator, Chao1, the predicted richness for the total area sampled is 173 ± 8.32 (SD) species. This indicates that the inventory was almost complete at the regional scale (92%). With similar proportions of captured species, rarefied richness value showed that species richness was highest in riparian swamp forest. Comparison of different sites revealed that species composition was much more similar within the same vegetation type than among different vegetation types. Assemblage composition differed the most between riparian swamp forest and plantation. Guild structure varied considerably in relation to the structural quality of vegetation.