Primarily nectarivorus. Lesser Violeatear "visits flowers of many herbs, shrubs, epiphytes, and trees" (Stiles and Skutch 1989). Specific sources of nectar include herbs such as Lobelia, shrubs such as Centropogon, Cuphaea, Fuschia, and Stachytapheta, and trees such as Inga and Erythrina (Skutch 1968, Colwell et al. 1974, Feinsinger 1976, Hilty 2003, Barrantes et al. 2008). Like other hummingbirds, Lesser Violetear also consumes small insects (Remsen et al. 1986).
Lesser Violetear is flexible in its foraging behavior, depending upon flower density and the presence of competing species. Where favored flowers are tightly clustered, violetears defend small feeding territories (Colwell 1973), but when flowers are more dispersed, this species acts more like a traplining species, following a feeding route between scattered flowers or flower clusters (Feinsinger 1976).
Lesser Violetear forages for insects by gleaning them from foliage (Feinsinger 1976).