Accurately predicting rainfall thresholds that can trigger landslides is crucial for effective risk management and early warning systems. This study applied TRIGRS (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability model) to determine rainfall thresholds for landslide initiation in Muong Hoa Valley, Vietnam. By assessing the factor of safety (Fs) for each grid cell and iteratively increasing rainfall intensity for fixed durations, critical intensity-duration (I-D) combinations were identified. The resulting dataset is fitted to a power-law equation to derive a predictive model for landslide initiation thresholds. The results show that landslides can be triggered after as little as 8 h of continuous rainfall at intensities above 17 mm/h, with lower intensities requiring longer durations. These findings provide a predictive framework for identifying critical rainfall conditions in the region, enhancing local preparedness and response. While the model offers valuable insights, uncertainties in soil parameters and hydrological conditions present challenges that need further investigation. This methodology can be adapted to other regions with similar conditions, supporting broader efforts in landslide risk mitigation.