Interspecific hybridization occurs naturally only under restricted conditions and is a phenomenon with evolutionary and agricultural implications. Production of viable pollen grains is required in at least one of the species involved, provided the other parental species is female-fertile. In this study, we assessed pollen viability in the South American native Saccharum villosum and in S. x officinarum (sugarcane), which are partly sympatric. Sex distribution in sugarcane hybrids and reproductive morphology of S. villosum were analyzed to verify potential conditions for interspecific hybridization. Five of the sugarcane hybrids were shown to be exclusive hermaphrodites, two of them protogynous and one protandrous, and three hybrids were shown to be gynomonoecious, all potentially able to receive and donate pollen. All hybrids have viable pollen grains, but at different degrees (ca. 4% to 62%). S. villosum produces more viable pollen than sugarcane in southeastern Brazil. Pollen grains in S. villosum are middle-sized (32-39 μm in diameter), monoporate, monadic, prolato-spheroidal, isopolar, with exine ornamentation consisting of ungrouped granules, being distinguishable from sugarcane pollen. Pollen grains in S. villosum are highly variable for the five internal traits measured, especially for nexine and tectum thicknesses. Seed development of S. villosum occurs before panicle emergence. A morpho-anatomical analysis of the germinated seed revealed that S. villosum has traits considered as derived within Poaceae, such as the lack of epiblast. However, this species is an early-divergent Saccharum member, based on a small relative embryo size. In conclusion, the absence of natural hybrids between sugarcane and S. villosum is more probably associated with either autogamy or agamospermy in the wild species rather than with pollen inviability or absence of pollen production in sugarcane.