Devastating natural disasters and their aftermath are known to cause psychological distress. However, little information is available regarding suicide rates following tsunami disasters that destroy regional social services and networks. The aim of the present study was to determine whether the tsunami disaster following the Great East Japan Earthquake in March 2011 has influenced suicide rates. The study period was from March 2009 to February 2014. Tsunami disaster-stricken areas were defined as the 16 municipalities facing the Pacific Ocean in Miyagi Prefecture. Inland areas were defined as other municipalities in Miyagi that were damaged by the earthquake. Suicide rates in the tsunami disasterstricken areas were compared to national averages, using a time-series analysis and the Poisson distribution test. In tsunami disaster-stricken areas, male suicide rates were significantly lower than the national average during the initial post-disaster period and began to increase after two years. Likewise, male suicide rates in the inland areas decreased for seven months, and then increased to exceed the national average. In contrast, female post-disaster suicide rates did not change in both areas compared to the national average. Importantly, the male suicide rates in the inland areas started to increase earlier compared to the tsunami-stricken areas, which may reflect the relative deficiency of mental healthcare services in the inland areas. Considering the present status that many survivors from the tsunami disaster still live in temporary housing and face various challenges to rebuild their lives, we should continue intensive, long-term mental healthcare services in the tsunami-stricken areas.