Breast cancer patients may present with patient delay or experience provider delay-2 factors which can lead to a late-stage diagnosis and poor prognosis. Mass disasters drastically change social structures, and have the potential to contribute to these delays. However, there is little information available on patient and provider delay related to cancer after disasters. In March 2011, an earthquake, followed by a tsunami and nuclear accident struck Fukushima, Japan. In July 2014, a 59 year-old Japanese widow, living alone, presented to our hospital with a lump and pain in her right breast, which had originally appeared in April 2011 and continuously deteriorated for 3 years and 3 months. She was diagnosed with stage IIIB right breast cancer. Detailed history revealed that she was exposed to social isolation in the aftermath of the disasters due to evacuation of her friends and daughter. Although she regularly saw her general practitioner, she did not disclose her breast symptoms for 1 year and 5 months, at which time she was falsely diagnosed with intercostal neuralgia. She did not seek further medical attention for the breast symptoms for another 1 year and 10 months, despite multiple clinic visits for unrelated reasons. The present disasters, particularly the nuclear disaster, seem to have led to the social isolation of local residents, reducing their opportunities to discuss health concerns with others and seek subsequent medical attention.This case highlights that social isolation may contribute to patient and provider delay in breast cancer patients, as accentuated in this disaster setting.