Base-layer fabrics play a vital role in ensuring thermophysiological comfort within military clothing systems, especially in extreme environments where optimal performance is crucial and heat stress poses a significant challenge. This study assessed the thermal comfort performance of twenty advanced base-layer fabrics, with a focus on their potential application in military base-layer shirts designed for hot environments. Standardized laboratory tests are used to determine comfort related parameters: fabric weight, thickness, Overall Moisture Management Capacity (OMMC), thermal resistance (Rct), water vapor resistance (Ret) and thermal heat flux (Qmax). Fabric code “BL3” emerged as the most promising candidate with desirable thermal comfort properties, offering optimal moisture (sweat) management, and skin-cooling properties while maintaining compatibility with military garment specifications. These findings provide a data-driven framework for optimizing base-layer selection in Military clothing systems and support the integration of emerging textile technologies to enhance operational effectiveness in variable environmental conditions.