Diet composition of spiders may depend on several factors, such as the relative abundance of potential prey, microhabitat selection, structure and physical properties of webs, adaptations to attract specific prey, among others. Variation in diet composition is probably highly influenced by individual's spatial distribution and web design. In this study, we evaluated the population trophic niche breadths of two sympatric cobweb spiders, Nihonhimea tesselata (Keyserling, 1884) and Tidarren haemorrhoidale (Bertkau, 1880) (Theridiidae). These species build distinct webs in an area of Eucalyptus monoculture in southeastern Brazil. We collected their prey and also recorded parameters of webs like a height from the ground, distance from tree trunks, and distribution across the Eucalyptus stand. The diet of the two species was highly distinct. However, diet similarity was not correlated with the distance between webs. There was also no spatial segregation between species within the forest stand. However, N. tesselata used more distal portion of Eucalyptus branches than T. haemorrhoidale, which usually attached several threads to the tree trunk. In addition, diet restriction of T. haemorrhoidale may also be determined by the use of gumfooted threads attached to tree trunks (predominantly capturing ants), while aerial webs constructed by N. tesselata are more efficient at intercepting several groups of flying insects. Together, these differences in microhabitat and web design allowed effective resource partitioning among these two dominant predators in the studied plantation forest.