Kangaroo rats are reported to have a mutualistic relationship with harvester ants through facilitation of burrow establishment, creation, and persistence. The relationship can, however, become more complex. We report observations of the giant kangaroo rat (Dipodomys ingens), a state and federally listed endangered species, repeatedly kleptoparasitizing harvester ants from a nearby nest in the Carrizo Plain, California. Though the relationship between kangaroo rats and harvester ants has been studied extensively and is believed to be mutualistic, under certain conditions this relationship can follow an alternate path of parasitism.