Goldenseal (Hydrastis canadensis L.) is an herbaceous perennial species that is becoming more rare within its range. Hydrastis canadensis populations are highly isolated and pollen flow between these populations may be restricted. I examined the breeding system of H. canadensis to determine if it may be limiting seed set due to increasing isolation of individuals and populations from one another. I tested fruit set in treatments designed to detect the presence of apomixis, passive autogamy, active autogamy, short distance outcrossing and long distance outcrossing. No fruit set occurred in flowers that were emasculated and bagged, suggesting the species is incapable of apomixis. However, low rates of fruit set were found in all other treatments, suggesting a mixed mating system in which both selfing and outcrossing may occur. Pollen transfer between highly isolated populations can result in fruit set, as can within-population pollen transfer. The breeding system type appears unlikely to be a major factor limiting the distribution or abundance of H. canadensis. However, overall low rates of fruit set may be important demographically.