<p>Several studies have shown effects of temporal variation on ecological interactions such as those involving ants and plants bearing extrafloral nectaries (EFNs), however, little is known about how climate shapes the structure of these interactions in tropical rainforests. We specifically investigated whether rainfall seasonality in tropical rainforests influences the organization of ant-plant interaction networks mediated by EFNs, in terms of the number of interactions, network size, network specialization, diversity of interactions, and nestedness (using both binary and weighted data). We collected ants foraging on EFN-bearing plants in ten forest fragments situated in the west of the state of Acre, in the Brazilian Amazon. These ant-plant interactions were recorded in both dry and rainy seasons, resulting in a total of 20 ant-plant networks (n = 10 networks sampled in the dry season and n = 10 in the rainy season). We observed that network size and network specialization were not affected by rainfall seasonality, however we found that the diversity of ant-plant interactions was higher in the rainy season, while the number of ant-plant interactions and nestedness was higher in the dry season. We also observed that the central core of highly interacting ant species tends to be more stable than the central core of highly interacting plant species between dry and rainy seasons. In short, our results indicate that rainfall seasonality is a determining factor shaping the organization of ant-plant interaction networks in tropical rainforests.</p>