Stress is an inevitable part of life. It is a universal phenomenon and general experience of human which is necessary for his/ her survival and growth. It affects everyone irrespective of age, gender, race, economical condition or educational level. Although stress can be natural and necessary, if it is strict, continuous and repetitious and an individual is not able to respond to it effectively or if supportive sources are limited, it becomes a negative phenomenon which brings about physical and psychological disorders. The present study aimed to determine occupational stress level and conditions causing stress among nurses of educational hospitals in Qazvin Province. This is a sectional study on 194 nurses working in health care centers of Qazvin Province. Demographic questionnaire and Philip Rice's occupational stress questionnaire were completed by the nurses. In addition, they were requested to answer four more questions about insomnia and then the data was collected and analyzed using SPSS statistical software. Occupational stress has very high prevalence among nurses. The study showed that 91/2% of them experienced high levels of occupational stress. There is a significant relation between wards and occupational stress. In addition, the most important stressors among the nurses were recognized and the ways they respond to them were also studied. Moreover, the relation between the nurses' occupational stress and insomnia was examined. This study showed that the level of occupational stress among nurses was significant and there was a clear and meaningful relation between stress and the ward they work in. Among the stressors were physical tiredness due to work, emergency situations, heavy workloads and performing tasks requiring less knowledge and last but not least having multiple chiefs. It was also found out that nurses' occupational stress played a pivotal role in their insomnia status.