The clusioid clade is one of the major subclades identified within the large, diverse rosid order Malpighiales, using molecular data. However, nonmolecular synapomorphies are unclear, and more comparative data are needed to elucidate deep relationships within the order. In this article, pollen and tapetum characters are reevaluated in relation to recent hypotheses of phylogenetic relationships within clusioids. This is done to shed light on the evolution of pollen and tapetum, particularly the evolution of pollen dyads, and also to assess the potential utility of pollen and tapetal characters in the systematics of the clusioids. The comparative morphology of pollen and tapetum is examined in selected taxa from Bonnetiaceae (Bonnetia), Calophylaceae (Caraipa), Clusiaceae (Clusia, Garcinia), Hypericaceae (Hypericum), and Podostemaceae (Podostemum). Pollen and tapetum characters in clusioids and selected outgroups are tabulated, based on both original observations and an extensive literature search, and then optimized onto a recent molecular phylogeny. The optimizations indicate that unusual pollen dispersed as dyads has evolved from monads in the late-branching Podostemoideae (Podostemaceae) clade. Relatively small-sized pollen ( μm) is a potential synapomorphy for Hypericaceae and Podostemaceae, supporting the putative sister relationship between these two families, and pollen with circular or elliptic endoapertures is a potential synapomorphy for Bonnetiaceae. Several pollen characters (size, shape, apertures, and sculpture) indicate that Weddellina (Weddellinoideae: Podostemaceae) is more closely related to Hypericaceae than are Tristichoideae. Irregular granular exines have arisen several times independently within clusioids. A high level of polymorphism occurs in pollen characters in Clusiaceae and is probably related to high levels of diversity in floral morphology, pollination mechanisms, and pollinators, particularly in Clusia and Garcinia. By contrast, pollen of Podostemoideae is relatively uniform, despite developmental differences in microsporogenesis type and the presence of dyads. This may reflect evolutionary canalization or convergent evolution in these enigmatic aquatic plants.