Solid concrete slabs are very important structural members in building and construction because traditional slabs reinforced with steel carry the load and transfer it to the beam. However, steel reinforcement corrodes, which affects the integrity of concrete structures by reducing their strength and serviceability, thus leading to failure. For this reason, non-corrosive Glass Fibre Reinforced Polymer (GFRP) bars are an effective alternative reinforcement in concrete slabs. Moreover, concrete slabs are very heavy and make up a high percentage of the dead load in a building structure; this in turn means that more concrete is needed. There is therefore a crucial need for lighter slabs with a better structural performance and this can be provided by Hollow Core Slabs (HCS). However, HCS slabs contain internal voids which cause premature shear failure and the walls to collapse. In response, a hollow Composite Reinforcing System (CRS), with four flanges to improve their bond to concrete, has been developed to stabilise the voids in concrete members. This study investigates the flexural behaviour of concrete slabs reinforced with FRP bars and CRS. Four slabs (a solid slab reinforced by GFRP, a hollow slab reinforced by GFRP, a slab reinforced by GFRP and CRS, and a slab reinforced by steel and CRS) were tested under four-point static bending to better understand the structural performance of this new construction system. The results proved that solid and hollow slabs behaved similarly due to the voids located in the areas under compressive stress, and that CRS enhanced the structural performance of hollow core concrete slabs by 85%, while the stiffness of GFRP reinforced hollow slabs and the load carrying capacity increased by 32%. CRS was found to be more compatible with GFRP bars than steel bars due to their similar modulus of elasticity. A theoretical evaluation of the behaviour of concrete slabs reinforced with GFRP bars and CRS using the Fibre Model Analysis was also carried out. This FMA considered the tensile strength of concrete and the flanges of CRS, and found that the predicted failure load was only 13% less than the failure load measured experimentally. Important parameters such as the number of voids, the compressive strength of concrete, and the reinforcement ratio were also analysed with regards to the overall behaviour of the slabs. The results of this study provide useful information for the construction industry on the structural performance of concrete slabs utilising CRS and for the effective and safe design of such a construction system.