Insomnia is one of the most common sleep disorders, characterized by difficulties in sleep initiation, sleep maintenance or early morning awakening. Sleepiness is also such issues that associated with driving accidents, work accidents, and reduces efficiency and numerous interpersonal difficulties. The aim of the present study is to evaluate the severity of insomnia and sleepiness workers who were exposed to extremely low frequency magnetic fields in one of thermal power plants in Tehran as a case-control study. In order to exposure evaluation of these groups, resultant magnetic flux density with extremely low frequency was measured with TES-1394 device in workplace and commuting of worker. Insomnia severity index and Epworth Sleepiness scale was used to assess insomnia and sleepiness status and depression. The maximum exposure in case and control group was 2.95 µT and 0.17 µT, respectively. There are significant differences in extremely low frequency magnetic field exposure between case and control groups (p