This study presents experimental and analytical research that focused on the behaviour of carbon-fibre-reinforced polymer (CFRP)-strengthened flat-slab specimens for punching shear enhancement. Seven 0.75-scale flat-slab specimens representing interior slab-column connections with different column aspect ratios varying from 1 to 3 were tested. The results revealed that increasing column rectangularity had a detrimental effect on column punching strength of all specimens. A strength increase of at least 30% was obtained for the CFRP retrofitted specimens compared with the companion reference specimen. Three-dimensional finite-element models were successful in providing reasonable estimates of load-deformation behaviour and strains. Based on these results, CFRP strains at failure and the punching failure mechanism are discussed.