No statistical data is available on the number of employees working on night shifts in Turkey. Working on shifts is associated with decreased sleep time, decreased daily sleep quality, and decreased alertness during night shifts. Increased incidences of cardiovascular disorders, peptic ulcers, and some types of cancer in shift workers are well known. Exposure to light at nighttime suppresses melatonin production. In non-synchronized circadian rhythm, disturbed melatonin secretion may lead to excessive sleep, hunger for carbohydrates, and weight gain. Melatonin is the hormone that governs sleep. It seems to be the key regulator of the sleep/wake rhythm. Exposure to light at night and disturbance of the circadian rhythm contribute to the health problems of night shift workers by disturbing melatonin production. In this review, the definitions of social jetlag, delayed sleep phase syndrome, and insomnia will be discussed. Sleep disorders in psychiatric diseases will be reviewed. Melatonergic drugs available on the market will be listed, including their contraindications and side effects. The physiopathology of sleep, sleep disorders, depression, and melatonin will be given with an extended discussion. Two recent reviews about the effect of melatonin on sleep patterns will be discussed. Finally, other treatments for sleep disorders will be summarized. In conclusion, in shift workers, sleep problems are a complex subject in which multiple pathophysiological mechanisms play roles. The double-blind randomized controlled studies, systematic reviews, and meta-analyses that have been conducted can provide only weakly positive data about the beneficial effect of melatonin use in shift workers. In the future, multi-centered and multi-participant studies will shed more light on this issue.