Fiber-reinforced composites (FRC) have gained widespread recognition in the aerospace, automotive, and energy industries due to their exceptional strength to-weight ratio. However, comprehending their performance within varying environmental contexts poses a multifaceted challenge. Specifically, the influence of humidity, temperature fluctuations, and freeze–thaw cycles on the structural integrity of FRC components requires careful examination. This research work seeks to provide insights into the effects of humidity, temperature, and freeze thaw cycles on FRC inter-laminar regions and the critical matrix/fiber interface. The experimental methodology employed includes a comprehensive array of techniques, such as thermal analysis, X-Ray tomography, and ILSS mechanical testing. Through these methods, an effort is made to discern the material’s response to the environmental variables. Carbon-reinforced composites exhibited a shear strength reduction of 16.9% at 80 °C, and glass-reinforced composites displayed a reduction of 18.4%. Further increasing the temperature to 125 °C resulted in a reduction of 32.5% for carbon-reinforced composites and 38.8% for glass-reinforced composites. In hot-wet conditions, which combine humidity saturation and a testing temperature of 80 °C, the shear strength reductions were the most pronounced, with a reduction of 48.7% for carbon-reinforced composites and 60.2% for glass-reinforced composites. Moreover, freeze–thaw cycle has been performed. The findings of this research endeavor hold profound implications for both the design and maintenance of FRC components. As FRCs continue to gain prominence in critical applications, an enhanced understanding of their behavior in diverse environmental conditions becomes increasingly imperative.