Background & objectives: Nursing is one of the important professions for public health. The purpose of the present research was to investigate Morningness- Eveningness in relation to sleep quality and occupational motivation in nurses working in health centers of Ardabil.

Methods: A descriptive-correlational design was used to conduct the study. The statistical population comprised of nurses working in the hospitals of Ardabil in 2015, in which using the cluster sampling method, 198 nurses working in Ardabil’s hospitals were selected to the study. In order to collect data, the questionnaires of Pittsburg's sleep quality, Morningness-Eveningness (CSM) and the scale of occupational motivation were used. The multi-variant variance analysis and pursued test were used to analyze the data.

Results: Data analysis identified Morningness-Eveningness of the 198 nurses participated in the study as follows: morning-type (20%), evening-type (14%) and 66% of the subjects had a combination of morning-type and evening-type (mixed-type) of work shifts. By comparing three groups of evening-type, mixed-type and morning-type was found that evening shift nurses have a lower sleep quality. Moreover, evening work shift nurses had a lower professional motivation in comparing with nurses who were working in morning and rotational shifts. Also, significant correlations were found between the Morningness with sleep quality and occupational motivation of the participants.

Conclusion: The results show that sleep problems is a major problem among nurses. This problem is greater among the nurses working in evening work shifts which can decrease the professional motivation of nurses. Attention to the circadian rhythms of individuals may help to reduce these problems.