Although we do not know the cause of death of most fossils, mortality is often associated with ecological stress due to seasonality and other stochastic events (storms, volcanism) that may have caused shifts in feeding ecology preceding death. In these instances, dental microwear, which reflects feeding ecology in a narrow window of time, may provide a biased view of diet. Mesowear, another dental wear proxy based on the morphology of worn cusps, requires macroscopic amounts of dental wear and reflects diet for a longer interval and may be less prone to bias from near-death ecological stress. We compared congruence between microwear and mesowear of North American fossil rhinocerotid mass death assemblages and hunted collections of modern rhinocerotids to test the hypothesis that fossil assemblages yield more incongruous microwear and mesowear results as a result of near-death ecological disturbances. In extant rhinos, both microwear and mesowear are associated with diet and height of the feeding environment. Mesowear and microwear in the modern rhinocerotid collections are statistically correlated with strong relationships between average mesowear scores and labially distributed dental microwear. In contrast, a statistical relationship between mesowear and microwear was not observed among the fossil rhinocerotid assemblages. Mesowear suggests the fossil rhinos had low abrasion diets, suggesting they fed from clean, possibly tall vegetation. Some, but not all mass death assemblages produce microwear data with excessive scratches and/or pits compared to expectations based on mesowear results, suggesting that dental microwear was altered shortly before death in some but not all of the fossil assemblages. The dental wear proxies available to paleoecologists provide a mosaic of dietary evidence reflecting diet over long (mesowear) and more abbreviated (microwear) periods of time that, together, provide a richer understanding of feeding ecology and its relationship to environment, seasonal change, and other ecological disturbances.