This study presents a comprehensive evaluation of the minimum detectable activity (MDA [1]) for 134Cs in soil samples using Compton suppression [4,6] gamma-ray spectrometry [2–4]. A high-purity germanium (HPGe) detector coupled with a NaI(Tl) anti-coincidence system was employed to reduce the Compton continuum and improve detection sensitivity. The detector system was modeled using the PENELOPE [5,29] Monte Carlo [5,7,13] code, and the simulated full-energy peak efficiencies were validated against experimental measurements. The agreement between simulation and experiment was within ±5%, with a normalized root mean square error (NRMSE) [30] below 5%, confirming the reliability of the detector modeling. Activity determination was performed using two independent gamma-ray peaks at 604.7 keV and 795.8 keV. Gaussian fitting [16] combined with ROI-based analysis enabled accurate extraction of net peak areas, and the consistency between the two peaks provided cross-validation of the results. The application of Compton suppression [4,6] resulted in a significant reduction of the continuum background, particularly within the regions of interest. Consequently, the MDA [1] values were reduced by approximately 46–56%, with an average reduction of about 50% compared to the unsuppressed condition. These results demonstrate that Compton suppression [4,6] significantly enhances detection sensitivity and provides a robust and reliable approach for low-level environmental radioactivity analysis