Montezuma Oropendola is omnivorous, probably feeding primarily on arthropods and small vertebrates, but also consuming fruits, seeds, and even nectar (Stiles and Skutch 1989). Among the larger prey captured by this species are juveniles of Black-faced Grosbeak (Caryothraustes poliogaster) (Wolf 1971) and of Blue-gray Tanager (Thraupis episcopus) (Sánchez-Monge and Calderón Mesén 2012), and a rat (Nyctomys sumichrasti) (Enríquez-T. and Barksdale 2013). Among the fruit consumed by Montezuma Oropendola are Cecropia catkins and bananas (Skutch 1954). Flowers on which these oropendolas feed include Marcgravia species, which it is believed to pollinate (Tschapka and Helversen 1999).
Nestling oropendolas are provisioned with large arthropods (primarily spiders and orthopterans) and small vertebrates (frogs and lizards), along with some fruit (Webster 1994a).