The overall compressive behaviour of grouted concrete hollow block prisms is dependent on the mechanical properties of both the masonry block and its grout. Grout is typically characterized by exhibiting greater longitudinal and lateral strains when compared to concrete blocks. Hence, a direct consequence is a composite-action incompatibility due to grout-to-block differential strain response under compressive loading. In order to enhance the overall composite behaviour, adding glass fibres to the grout mixture is considered in this study. The fibre-reinforced grout is expected to reduce grout longitudinal and lateral strains to be more consistent with the concrete block, which will result in better control of the cracking propagation and thus enhancing the overall ductility. This study investigates the effect of adding glass fibres to grout mix on the compressive strength and strain of the concrete masonry prisms. The presented experimental program involves testing of 36 fully grouted half-scale masonry prisms, with different glass fibre ratios (0%, 0.03%, 0.06%, and 0.10%). Twenty-four prisms were of one block thickness and two blocks in height, divided into two groups of normal and high strength blocks. The remaining twelve prisms were two blocks in thickness and five blocks in height with normal strength blocks. The prisms were tested concentrically up to failure. Results demonstrated that the addition of glass fibres to the grout enhanced the crack control as well as the post-cracking performance. The influence of adding glass fibres to the grout on increasing the masonry prisms' compressive strength was evident at high fibre percentage (i.e., 0.10%) by approximately 9.8%, 10.1 %, and 39% for the high strength two-block high specimens, normal strength two-block high specimens, and normal strength five-block high specimens, respectively.