Thermal insect treatments can be an effective method of controlling cryptic insect pests, particularly bed bugs, in residential settings. The treatments require high heat over a sustained timeframe. Residents are not present during treatment but return after completion. An unexpected death was investigated following heat treatment for bed bugs in the home of an elderly female, found with a postmortem axillary temperature of 106.2°F (41.2°C) approximately 8 h after returning home. The cause of death was classified as hyperthermia with a contributory cause of hypertensive cardiovascular disease. The manner of death was an accident. The decedent had medical history and medications that could have impaired her ability to dissipate heat. Furthermore, the air conditioning inside the residence was not functional following treatment. Recommendations including education regarding heat stroke and treatment, re-entry timeframes, and/or temperature thresholds are suggested to reduce the risk of heat-related injury or death in vulnerable populations.