The 2004 Indian Ocean tsunami was one of the world’s worst tsunamis and caused devastating damage in many Asian countries. Then, in 2011, Japan was hit by a tsunami that was generated by the greatest earthquake in the country’s history. This paper discusses the damage caused by these tsunamis and subsequent reconstruction. Introduced first are the experience gained and lessons learned for future tsunami mitigation, such as tsunami awareness, proper evacuation building and the memorial parks created in the countries affected by the 2004 tsunami (Indonesia, Sri Lanka and Thailand). Second, human casualties and building damage are discussed using fatality ratios and fragility curves, respectively. These analyses show that experience and awareness help reduce human casualties in the Sanriku area, and wooden houses damaged by the 2011 tsunami fared better than in previous historical events. The damage by the 2011 tsunami to structures designed to protect against tsunamis is summarized. Most of these structures could not withstand and protect from the tsunami because they were not designed for such a large tsunami as expecting of such great event. Finally, examples of ongoing reconstruction in Japan are introduced. Most reconstruction efforts were planned after considering the lessons learned from the tsunami’s impact, and the towns in question are now strengthening their disaster prevention-related plans to be better prepared for future tsunamis.