We often study the outcomes of species interactions, whether they be predation, competition, or mutualism, at one site in a single year. However, we increasingly recognize that species interaction outcomes are not static, but context dependent by varying along many ecological axes. Here, I asked to what extent and along what axes are ant-plant protection interactions, in which plants provide rewards for ants that in turn defend plants from herbivores, context dependent. First, a meta-analytic summary of published studies on ant-plant protection interactions revealed that interaction outcomes are on average mutualistic, and context dependency occurred due to plant reward type (domatia vs food bodies vs extrafloral nectaries), ant species richness, and latitude. Second, in a case study in the Sonoran Desert, extrafloral nectar production caused context dependent mutualistic and antagonistic ant-plant interactions, despite largely commensalistic interaction outcomes. These results suggest some ecological axes resulting in context dependency in mutualisms.