Differences in species richness and species composition of spiders associated with aquatic macrophytes of different structural complexities were examined in the Pantanal floodplain of Mato Grosso do Sul, Brazil. The plants studied were Nymphaea amazonum (Nymphaeaceae), Salvinia auriculata (Salviniaceae), Echinodorus paniculatus (Alismataceae) and Eichhornia azurea (Pontederiaceae), whose classes of complexity were determined based on their leaf and branch densities, vertical structure, and height. Data were collected from 62 monospecific plant patches in temporary lentic environments. A total of 235 spiders of 33 species in 13 families was collected. Nymphaea amazonum, the plant with the lowest complexity class, did not provide adequate sites for the establishment of spiders, and only four individuals of four spider species were found on its patches. Salvinia auriculata and E. paniculatus shared the intermediate class of complexity, but showed statistically significant differences in composition and richness of spider species. In E. paniculatus, greater height and lower leaf and branch densities favored the establishment of web weavers, whereas the smaller height and higher density of S. auriculata promoted the occurrence of wandering spiders. Eichhornia azurea, the plant with the highest complexity class, presented the greatest number of unique spider species, differing from the other plants in spider species composition. Results indicate that richness and composition of spider species associated with aquatic macrophytes in the study site are influenced by the structural complexity of these plants.