Cratylia argentea is a high-quality forage legume shrub, with particular potential for the subhumid tropics owing to its adaptation to acid and infertile soils and drought tolerance. However, lack of knowledge about the ability of this species to self-pollinate makes purity maintenance of accessions difficult. Studies were conducted to investigate whether the gametes of C. argentea flowers are self-compatible, and to verify the dependence of reproduction on insects. Pod set and seed production were assessed in a pollination experiment with 4 treatments (spontaneous self-pollination, artificial self-pollination, insect pollination and artificial cross-pollination). Our results (0–1.2% pod set after selfing, 3.4% after insect pollination and 20.3% after artificial crossing) suggest that C. argentea is mostly self-incompatible. Seed:ovule ratios were 0.63 with insect pollination and 0.78 with artificial crossing. We found that pollen grains mature before the stigma becomes receptive, which suggests that the species is cross-pollinated. We also found evidence that C. argentea depends on large solitary bees for pollination, based on flower structure and the stigma becoming receptive only after tripping of the flower. Xylocopa frontalis and 2 Centris species were identified as key pollinators. In view of its simplicity, the research procedure utilised is suggested for other tropical legume species pollinated by large insects.