Castilleja (the “paintbrushes”) is a genus of over 200 species of American wildflower whose systematics has been an ongoing challenge. Because of their hybridization potential and taxonomic difficulties, including species descriptions with overlapping qualitative and quantitative traits, many species are challenging to identify in the field and from preserved specimens. Morphology has largely driven species delimitation in Castilleja, including seed coat characteristics; however, pollen morphology, an important trait associated with pollination biology in angiosperms, has not been examined in the group. Pollen morphology has been used in the characterization of higher- and lower-order taxa, and pollen surface structure is potentially related to pollination syndromes, dispersal methods, and pollen-stigma interactions, which may affect reproductive potential. In this study, light and scanning electron microscopy of pollen from a species complex native to the California coast were used to describe their morphology, assess whether pollen morphology varies according to current taxonomy, and determine whether pollen morphology can be used to inform species boundaries in Castilleja.