This study was conducted to investigate the effect of nurses' Machiavellian and deontic justice personality on the tendency to make medical errors. Additionally, conducted to investigate the other factors associated with nurses' tendency to make medical errors. This cross-sectional study consisted of 345 nurses working in a state university medical faculty health application and research hospital, and data were collected using the Medical Error Tendency in Nursing Scale, the Machiavellian Personality Scale, and the Deontic Justice Scale. Machiavellian and deontic justice personality of nurses effect in low level their tendency to make medical errors (R = 0.284, p = 0.001). As the nurses' Machiavellian tendencies increased, their propensity toward making medical errors also increased. The increase in Nurses' deontic justice reduced their tendency toward medical errors (p < 0.05). A significant difference was found between nurses' mean tendency to medical errors scores and their age, working life/years, the number of night shifts, the daily number of patients provided with care, the status of working in the COVID-19 service, and the status of having received education on medical errors (p < 0.05). Nurses' Machiavellian tendencies and deontic justice approach affect their propensity to make medical errors. Nurses who have a Machiavellian tendency and poor deontic justice have a high tendency to make medical errors. Nurses' age, working life/years, the number of night shifts, the daily number of patients they provide care for, working in the COVID-19 service, and having received education on medical errors were the other factors affecting their tendency to make medical errors. This study demonstrated that nurses' personality traits can cause medical errors. Generations are changing in the world and personality are also changing. Therefore, including personal development in nursing education could be a positive approach for medical errors.