The Bili-Bili Dam, located in Gowa Regency, South Sulawesi, Indonesia, is a critical infrastructure project that supports water supply, irrigation, flood control, and hydroelectric power generation for the region, particularly benefiting Makassar City and its surrounding areas. Given its vital role in socio-economic development, ensuring the dam's structural integrity is paramount. This study focuses on estimating the vibration characteristics of the Bili-Bili Dam using microtremor observation, a non-destructive testing method, to assess its structural condition and seismic site effects. Microtremor measurements were conducted at 16 points, including 9 at the dam's crest and 7 at its base, with each recording lasting 20 min. The results from the spectral ratio of top and base measurement revealed that the dam's natural frequency ranges between 2 and 5 Hz. Analysis of the vibration data indicated that the perpendicular direction to the dam's axis is dominant, likely influenced by the reservoir's dynamic pressure, as supported by rose diagram results. However, the left wing of the dam shows a potential resonance risk due to the similarity between the soil and structural natural frequencies, which could amplify seismic vibrations during an earthquake. These findings highlight the importance of continuous monitoring the dam to mitigate resonance risks. The study demonstrates the effectiveness of microtremor observation as a tool for assessing the structural health of dams, providing valuable insights for ensuring the long-term safety and functionality of the Bili-Bili Dam amidst geological and seismic challenges.