To improve disaster preparedness, we investigated the response of medical relief activities managed by Iwate Prefectural Miyako Public Health Center during the post-acute phase of the Great East Japan Earthquake and Tsunami on March 11, 2011. The study divided the post-disaster period into three approximate time segments: Period I (time of disaster through late March), Period II (mid-April), and Period III (end of May in Miyako City, early July in Yamada Town). We reviewed records on medical relief activities conducted by medical assistance teams (MATs) in Miyako City and Yamada Town. Miyako Public Health Center had organized a meeting to coordinate medical relief activities from Period I to Period III. According to demand for medical services and recovery from the local medical institutions (LMIs) in the affected area, MATs were deployed and active on evacuation centers in each area assigned. The number of patients examined by MATs in Miyako rose to approximately 250 people per day in Period I and decreased to 100 in Period III. However, in Yamada, the number surged to 700 in Period I, fell to 100 in Period II, and decreased to 50 in Period III. This difference could be partly explained as follows. In Miyako, most evacuees had consulted LMIs which restarted medical services after disaster, and the number of LMIs restarted had already reached 29 (94% of the whole) in Period I. In Yamada, most evacuees who had consulted MATs in Period I had almost moved to LMIs restarted in Period II. During the same time, a division of roles and coordination on medical services provision was conducted, such as MATs mainly in charge of primary emergency triage, in response to the number of LMIs restarted which reached 1 (20%) in Period I and 3 (60%) in Period II. Following Period III, more than 80% of patients in Miyako had been a slight illness, such as need for health guidance, and the number of people who underwent emergency medical transport reached pre-disaster levels in both locations. These results suggest that demand for medical services of evacuees declined to a stable level in an early stage of Period III. Using the above findings, one might justify supporting local medical institutions' recovery earlier. Then, medical relief activities might be finished properly. This study shows useful perspectives in the response of medical relief activities during post-acute phase after disaster and the importance of establishing systems for information management that apply these perspectives.