Abstract : Shift workers refers to a work schedule that involves irregular or unusual hours, such as morning and evening shifts, as opposed to regular day work. Sleep disturbance is the main problem faced by night shift workers, especially security workers. Growing evidence has shown that vitamin D plays a role in sleep regulation. Therefore, vitamin D supplementation may have positive effects on sleep disturbances, including decreased sleep latency, increased sleep efficiency, and longer sleep duration. This research is a quasi-experimental study with a case-control design. The intervention group was the Security Unit which was given Vitamin D at a dose of 1000 IU and standard care at Prof. Dr. I.G.N.G Ngoerah. The control group is a Security Unit unit that is given standard care without giving vitamin D 1000 IU according to the standard of care at Prof IGNG Ngoerah Hospital. The mean age in the intervention group was 41.7 ± 9.7 and that in the intervention group was 42.6 ± 8.8. the highest level of education is high school and the majority of subjects are married. The median sleep quality score after the intervention fell to 2.0 (IQR 2) with the median improvement in sleep quality score in the intervention group being 7.0 (IQR 3). Whereas in the control group the average score for sleep quality after 8 weeks was 6.0 (IQR 1) with an average score for improving sleep quality was 0.0 (IQR 1). Based on multivariable analysis, the acquisition of vitamin D significantly affected sleep quality improvement (B=5.9, 95% CI=4.809-6.981, P<0.001) while sleep quality improvement was not significantly affected by age (P = 0.992), last education level (P = 0.683) and marital status (P = 0.616). Providing vitamin D supplements can be a useful strategy to help improve sleep quality in security units who often work night shifts.