People living with mental illness are disproportionately affected by stigma in public environments and healthcare systems. Therefore, this quantitative correlational study aimed to explore the nurses’ attitudes towards people with mental illness in Oman. It also assessed the factors that influence nurses’ attitudes in providing health care in the Ministry of Health facilities. Additionally, this study examined the relationship between the demographic characteristics of nurses (age, gender, levels of education, years of nursing experience, and areas of nursing practice) and their attitudes towards people with mental illness. Methods: A total of 530 registered nurses, with a minimum of one year nursing experience, from Four governmental hospitals in Oman have participated in this study, and only 502 surveys were included in the study analysis. The participants were recruited via convenience and nonprobability sampling. The Opinions about Mental Illness Scale (OMI) and the Demographic Characteristics Questionnaire were used in the study. Results: A total of 530 registered nurses have participated in the study with a response rate of 94.7%. Demographic characteristics (age, levels of education, and years of nursing experiences) were significantly related to nurses’ attitudes towards people with mental illness. The findings of this study indicated that nurses who worked in mental health areas had more positive attitudes than nurses who worked in in other areas including medical-surgical and maternal and child health areas. Conclusion: Actions should be taken to foster positive attitudes towards people with mental illness, such as evaluating ways to do this in nursing curricula as well as incorporating programs to promote knowledge of mental health among practicing nurses, particularly general nurses.