The aim of this study was to delineate the multi-level relationships of individual registered nurse (RN) and nursing unit factors on missed nursing care. This was a quantitative model-building study using a descriptive, cross-sectional design. Surveys (N = 553) and administrative unit records from nurses in one hospital system undergoing merger were included. The results showed that 36% of the variation in missed nursing care is due to the unit context, with a corresponding 64% due to individual nurse differences. At the unit level, workload, skill mix, and critical unit type affected the amount of missed nursing care. At the individual nurse level, more experience, supplies problems, communication problems, and involvement in errors of commission all increased the perception of the amount of missed nursing care. Education level was not related to the amount of missed nursing care. The findings highlight the importance of unit- and individual-level interventions to redesign hospital nursing care.