Mount Merapi is one of the most active volcanoes in the world, as evidenced by several major eruptions in 1768, 1822, 1849, 1872, and the most recent one in 2010. These events have significantly impacted structures and infrastructure, including health centers. Health centers serve as primary healthcare facilities and are located in areas adjacent to Mount Merapi. Based on their location, there are three health centers situated at the foot of Mount Merapi in the Sleman region of Yogyakarta. These health centers, namely Pakem, Turi, and Cangkringan, are at high risk of potential disasters, ranging from eruptions, cold lava flows, to landslides. In light of these circumstances, to maintain service quality and effective disaster response, a study on functional preparedness was conducted to assess the readiness level of these health centers. This study aimed to provide evaluation material for optimizing service quality. The research employed a quantitative analysis method, collecting numerical data to outline the preparedness level of the three health centers. The analysis results, achieved through manual calculations, indicated that Puskesmas Pakem exhibited the highest functional preparedness with a score of 0.45, categorized as "moderate." Puskesmas Turi scored 0.40, also categorized as "moderate." On the other hand, Puskesmas Cangkringan scored 0.24, falling into the "low" category. In conclusion, two health centers fell into the "moderate" category, indicating that their safety levels were operational during disasters. However, risks to the safety of staff and patients still persisted, necessitating future interventions. Meanwhile, one health center fell into the "low" category, signifying its inability to function optimally during disasters and therefore requiring immediate interventions.