The buckling reliability of composite cylindrical shells under axial compression is examined, with particular attention to laminate stacking sequence and variability in material properties due to operational conditions such as hydrogen storage. Two laminate configurations, Z32 and Z33, are analysed using both analytical buckling formulations and finite element (Abaqus) simulations. The analytical model is implemented in MATLAB and validated against eigenvalue buckling predictions from Abaqus. To quantify the effect of material property variability, Monte Carlo simulations are conducted for three cases: (a) normally distributed variation in carbon fibre Young’s modulus, (b) variation in epoxy matrix modulus and (c) combined variability in both. Results show that while stacking sequence significantly influences the mean buckling load, matrix stiffness variability has a greater impact on reliability due to its higher coefficient of variation. The study highlights the need for robust stacking design and material control, especially for composite structures operating in temperature-sensitive environments. The presented framework enables efficient reliability assessment and informs safety factor selection for advanced lightweight composite designs.