In this study we describe the ant assemblage visiting both foliar and bracteal extrafloral nectaries (EFNs) of Passiflora coccinea, investigate the protective role provided by ants against both herbivores and nectar-thief butterflies, and analyze possible fitness benefits for the plant (i.e., fruit and seed production) resulting from the presence of ants. Experiments and observations were performed in two Amazonian terra firme forest sites. Twenty-two ant species were recorded visiting the EFNs of P. coccinea. Camponotus aff. blandus was the most frequent and subordinate among the EFN-visiting ant species, accounting for 20% of the ant attacks on simulated herbivores (termites) and 50% on butterflies. Both the number of ant individuals and the number of species were positively correlated with the combined number of buds and flowers of P. coccinea. Moreover, ant protection behaviour against termites was stronger on flowers than on leaves. Finally, seed set almost doubled among fruits originating from ant-visited flowers as compared to flowers from which ants were artificially excluded. Our results suggest a protective role of ants for flowers of P. coccinea against both herbivores and nectar thieves, improving plant reproductive success.