Aim: This study aimed to illustrate the relationship between nurse staffing and missed care, and how missed care affects quality of care and adverse events in Thai hospitals.Background: Quality and safety are major priorities for health care system. Nurse staffing and missed care are associated with low quality of care and adverse events.However, examination of this relationship is limited in Thailand.Methods: This cross-sectional study collected data from 1188 nurses in five university hospitals across Thailand. The participants completed questionnaires that assessed the patient-to-nurse ratio, adequacy of staffing, missed care, quality of care and adverse events. Logistic regression models were used to estimate associations.Results: Higher patient-to-nurse ratio, poor staffing and lack of resource adequacy were significantly associated with higher odds of reporting missed care. Higher nurse-reported missed care was significantly associated with higher odds of adverse events and poor quality of care.Conclusions: Poor nurse staffing was associated with missed care, and missed care was associated with adverse events and lower quality of care in Thai university hospitals.