PURPOSE: The healthcare system is resource intensive, and many opportunities exist to reduce medical waste. Brachytherapists performing inherently resource intensive procedures are well poised to initiate the transition to sustainable, climate-smart care. The authors developed a quality improvement-based (QI) NorCal Brachytherapy Waste Audit Toolkit to guide medical waste reduction in brachytherapy procedures and provide climate health education. METHODS AND MATERIALS: The NorCal Brachytherapy Waste Audit Toolkit was validated through brachytherapy waste audits conducted at 2 neighboring hospitals between 2021 and 2023. Waste was categorized into biohazardous waste, nonbiohazardous waste, and anesthesia waste and was weighed and cataloged after each procedure using a standard template by auditors not involved in the brachytherapy case. Findings were analyzed for key drivers of waste production and high impact interventions were selected. RESULTS: Postaudit results demonstrate biohazardous waste reduction of greater than 50%, elimination of over 90% improper biohazardous waste sorting, cost savings ( .22/kg) and a reduction in landfill waste by over 20%. The Toolkit was made public online and over 18 months, was accessed by 34 distinct individuals from 21 healthcare organizations across 7 countries and led to waste reduction projects in multiple specialties including radiation oncology, emergency medicine, and pediatrics. CONCLUSION: A QI-based NorCal Brachytherapy Waste Audit Toolkit may help radiation oncologists and healthcare teams beyond radiation oncology reduce waste and contribute toward environmentally sustainable healthcare.