Introduced plants may compete for pollination with native species, leading to increased pollinator limitation for one or both species. In this study, I test the hypothesis that the introduced plant Euphorbia esula (Euphorbiaceae, leafy spurge) competes for pollination with the native prairie perennial Sisyrinchium campestre (Iridaceae, blue-eyed grass). A breeding system study revealed that Sisyrinchium is self- incompatible, potentially increasing its vulnerability to competition for pollination. Interspecific competition for pollinator visits occurred, as visit rates were lower for Sisyrinchium near Euphorbia than for Sisyrinchium more than 10 m from Euphorbia. However, supplemental hand pollinations of Sisyrinchium did not increase fruit or seed set either near to or far from Euphorbia, indicating that visits were not limiting. More than one- third of Sisyrinchium stigmas received Euphorbia pollen, but hand-pollination experiments detected no effect of Euphorbia pollen receipt on fruit or seed set, whether Euphorbia pollen was applied immediately or 2 h before application of Sisyrinchium pollen. Overall, this study suggests that Euphorbia does not reduce Sisyrinchium's pollination success despite competing for pollinator visits and being a source of heterospecific pollen on Sisyrinchium stigmas.