Concrete sandwich walls (CSWs) with wythes made of ultra-high-performance concrete (UHPC) have been recently studied, offering higher ductility and durability compared to conventional concrete walls. On the other hand, fiber reinforced polymer (FRP) composites have been implemented as shear connectors in CSWs to increase the panel’s thermal efficiency. This study aims to investigate the shear transfer and bond behaviour of UHPC-CSW with carbon-fiber (CFRP) shear connectors. A three-dimensional finite element (FE) model was developed and validated with two experimental sets, namely: pull-out tests on CFRP connectors embedded in UHPC, and shear transfer tests on conventional concrete CSWs. The model presented good calibrations with test results and predicted several of the key behavioural milestones. For the CSW shear tests, replacing the wythe with a UHPC one, resulted in an increase in specimen capacity. Using CFRP connector instead of steel slightly reduced the capacity but significantly increase inter-wythe slippage. The model will be further validated with experimental results and then used to conduct parametric study, exploring factors such as connector configuration, embedment depth in wythe, connector reinforcement ratio, wythe strength, and wythe thickness.