Natural disasters, such as earthquakes, are traumatic events causing both acute and enduring stress to affected individuals. Psychosocial consequences include posttraumatic stress disorder (PTSD), reactions of anxiety and depression and sleep problems. The island of Cephalonia in Ionian Sea is characterized by its high seismic activity. More specifically, this activity has been considered to be the highest of the Balkan Peninsula and Europe in general. In January and February of 2014 a long sequence of earthquakes, which included two main shocks of 6.1 Richter and 6.0 R, struck the island. The epicenter of the earthquake was the city of Lixouri. A long series of aftershocks measured ≥ 4.0 R followed these main shocks. In total, the number of earthquakes that affected those living in Cephalonia between January 26 and August 2014 when the present study took place, was 2055. Several damages concerning buildings, monuments and churches, stonewalls, road networks and port facilities occurred, but there were no human casualties. The aim of the present study was to assess sleep problems, insomnia in particular in the affected population after the two severe earthquakes in the island of Cephalonia. The assessment was made through the Athens Insomnia Scale (AIS). Sleep problems were assessed for two time points, i.e., retrospectively one month before and six months after the earthquake. In terms of psychopathology, anxiety (STAI - State anxiety) and symptoms of depression (CES-D) were more pronounced in our study population than the expected norm in the community. Correlations with depression (Center for Epidemiological Studies-Depression), anxiety (State-Trait Anxiety Inventory - State Anxiety) and PTSD symptoms (Impact of Event Scale-Revised) were investigated. A significant increase of sleep problems pertaining to insomnia was found (p<0.001). The most frequent complaints were difficulty with sleep induction, awakenings during the night, and sleepiness during the day. Higher STAI - State anxiety, CES-D, and IES-R scores were associated with greater likelihood of having insomnia six months after the earthquake. No other significant associations were detected with several recorded sociodemographic parameters. In conclusion the local population exhibited sleep disturbances 6 months after the earthquake. Sleep problems and ensuing next day dysfunctioning appear to be dependent on the existing psychopathology but independent of sociodemographic factors, and are potentially the result of constant worry due to the continuing seismic activity. Therefore, mental health providers should recognize and manage disordered sleep after earthquakes, although further studies are required to investigate the long-term impact of natural disasters on sleep.