In Japan, the most common reason for medical errors is a lack of cross-checking. To prevent errors, efforts to strengthen cross-checking behaviors are being adopted. However, time pressures also lead to errors, and increasing cross-checking activities leads to an increased workload and even greater time pressures. The purpose of this study was to identify working conditions that lead to time pressure for nurses, and to find ways to reduce time pressure and prevent subsequent errors. Self-reporting questionnaires were distributed over 10 days to 416 nurses working in 17 wards at two hospitals; 357 nurses (85.8%) responded anonymously, providing data on 2,150 person-days. In multivariate analyses, medical support services and the number of nurse calls answered were associated with subjective assessments of time pressures and nursing service delays due to busyness. Moreover, working the "evening-day shift" (when a nurse works a day shift after working the evening shift with no days off in between) led to a high level of fatigue before work and was associated with nursing service delays due to busyness. Reducing time pressures and preventing errors requires an adequate number of nurses, shift plans that consider rest periods and order of rotation, increased task discretion for nurses, and the prevention of chronic fatigue.