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Nectar production may disproportionately benefit male relative to female pollination success. In such cases, sexual selection is often suggested as the cause of asymmetric benefits, yet sexual selection in plants—particularly plants with hermaphroditic flowers—is infrequently tested empirically. Here, I used a protandrous herb with male‐biased nectar production (Chrysothemis friedrichsthaliana, Gesneriaceae) to test predictions from sexual selection theory. During three flowering seasons, I measured nectar production, pollinator visits, and male and female fecundity following different numbers of cross‐pollination events. In accordance with sexual selection predictions, (1) nectar production was greater during the male phase by at least 65%; (2) visits by the main pollinator (hummingbird Phaethornis striigularis) were limiting for part of the season, indicating that plants had to compete for pollinator visits; (3 …