Purpose: This study aimed to identify the degree of non-nursing tasks and nursing care left undone in integrated nursing care wards, and examine their relationships with nurses’ burnout, job satisfaction, turnover intentions, and medical errors. Methods: A cross-sectional questionnaire survey was conducted. Data were collected using self-report questionnaires from 346 nurses working in 20 wards of seven small and medium-sized general hospitals, and analyzed using multiple regression and multiple logistic regression analysis with the SPSS WIN 25.0 program. Results: The mean score for non-nursing tasks was 7.32±1.71, and that for nursing care left undone was 4.42 ± 3.67. An increase in non-nursing tasks (β = .12, p = .021) and nursing care left undone (β = .18, p < .001) led to an increase in nurses’ burnout (F = 6.26, p < .001). As nursing care left undone (β = .13, p = .018) increased, their turnover intentions also (F = 3.96, p < .001) increased, and more medical errors occurred (odds ratio 1.08, 95% confidence interval 1.02~1.15). Conclusion: Non-nursing tasks and nursing care left undone are positively associated with nurses’ burnout, turnover intentions, and the occurrence of medical errors. Therefore, it is important to reduce non-nursing tasks and nursing care left undone in order to deliver high quality nursing care and in turn increase patient safety.