A study on heat-related deaths in Brazilian urban areas from 2000 to 2018 reveals significant demographic and socioeconomic inequalities. The frequency of heat waves (HWs) increased from 0–3 per year in the 1970s to 3–11 per year in the 2010s, with higher rates in northern, northeastern, and central-western regions. Over 2000–2018, 48,075 excess deaths were attributed to HWs, far exceeding landslide-related deaths. The leading causes of heat-related deaths were circulatory and respiratory diseases and neoplasms. Critical regional differences were observed, linked to socioeconomic and health disparities, including lower life expectancy. Higher heat-related mortality was seen among low-educated individuals, blacks and browns, and older adults. The study highlights the need to strengthen primary health care and reduce socioeconomic, racial, and gender inequalities to mitigate heat-related deaths. Event-based surveillance did not detect a HW-mortality link, indicating that extreme heat is a neglected disaster in Brazil. The findings emphasize the importance of addressing climate change adaptation in urban areas to reduce health risks.A study on heat-related deaths in Brazilian urban areas from 2000 to 2018 reveals significant demographic and socioeconomic inequalities. The frequency of heat waves (HWs) increased from 0–3 per year in the 1970s to 3–11 per year in the 2010s, with higher rates in northern, northeastern, and central-western regions. Over 2000–2018, 48,075 excess deaths were attributed to HWs, far exceeding landslide-related deaths. The leading causes of heat-related deaths were circulatory and respiratory diseases and neoplasms. Critical regional differences were observed, linked to socioeconomic and health disparities, including lower life expectancy. Higher heat-related mortality was seen among low-educated individuals, blacks and browns, and older adults. The study highlights the need to strengthen primary health care and reduce socioeconomic, racial, and gender inequalities to mitigate heat-related deaths. Event-based surveillance did not detect a HW-mortality link, indicating that extreme heat is a neglected disaster in Brazil. The findings emphasize the importance of addressing climate change adaptation in urban areas to reduce health risks.