Autoclaved aerated concrete (AAC) has gained significant attention in construction due to its lightweight structure and superior insulating properties; however, its use in structural load-bearing elements is often limited by its relatively low mechanical strength. This study addresses this limitation by incorporating glass fibre-reinforced polymer (GFRP) laminates as face sheets and unsaturated polyester resin (UPR) pins as shear reinforcement, resulting in sandwich panels with AAC cores of varying thicknesses (17, 35, and 50 mm). Through experimental testing and analytical modelling, the shear capacity of these panels was investigated, specifically assessing the accuracy of several design guidelines (ACI 318, ACI 440.1R, ACI 440.4R, CSA S806, and Eurocode) in predicting the behaviour of both unreinforced and pin-reinforced configurations. Results indicate that the ACI 440.1R and ACI 318 provisions showed the closest alignment with experimental data for unreinforced panels, where the proposed stress limits in the shear reinforcement by ACI 440.1R offered more reliable predictions. In reinforced panels, adding UPR pins substantially improved load capacity, with ACI 440.1R, ACI 318, and Eurocode offering the most accurate predictions. Furthermore, the Eurocode approach demonstrated consistency in the calculation of the compression strut angle. Finally, this study underscores important distinctions among these design guidelines in accurately predicting shear behaviour for AAC-based sandwich panels with GFRP reinforcement, contributing to a better understanding of design methodologies for such systems.