AIM: The aim of the study was to examine the effect of the length of working hours on missed nursing care, quality of nursing care, and perceptions of the nursing practice environment. METHODS: A multicenter cross-sectional investigation using online questionnaires was conducted from April 2 to May 10, 2022, in twenty nine hospitals (13 Level-III hospitals and 16 Level-II hospitals). We collected data on the working hours of nurses and nurse-reported outcomes, including missed nursing care, quality of nursing care, and nursing practice environment. Restricted cubic spline (RCS) regression models were used to examine relationships between the hours per shift and nurse-reported outcomes. RESULTS: We investigated 12,703 nurses with a response rate of 97.33%. Nurses worked on average 7.72 (SD = 1.16) hours on the day shift and 8.92 (SD = 2.20) hours on the night shift, respectively. On the day shift, working 7.5 hours shift showed minimal missed nursing care; meanwhile, working 7-7.5 hours were correlated with the highest satisfaction of the nursing practice environment and better quality of nursing care. On the night shift, the highest missed nursing care was found for a working duration of 12 hours to the working 7 hours, with the lowest satisfaction while better quality was observed. The percentage of nurses who reported working overtime was 30.33%. Nurses who worked overtime reported lower satisfaction and poorer quality of nursing care on all shifts; moreover, working overtime showed the positive correlation to missed nursing care on the day shift, while on night shift was not statistically significant. CONCLUSION: Positive outcomes were observed for nurses who reported working 7-7.75 hours on the day shift and 12 hours (no more than 15 hours) on the night shift. . The results reemphasized the need for managers to reduce the working hours, overtime work, and the frequency of the night shift.