For the experimental investigation of the cracking behavior of carbon-reinforced concrete strengthening layers, large-scale, three-meter-long pre-damaged reinforced concrete slabs were analyzed using 4-point bending tests and digital image correlation. The reinforcement ratio, number of carbon grid layers, and bond properties of the steel reinforcement were varied. The results show a favorable cracking behavior of the strengthening layer, with smaller crack spacing and crack widths compared to the plain reinforced concrete section. The mean crack spacing in the stabilized cracking state ranged between 38 mm and 55 mm, corresponding to approximately two to three times the spacing of the carbon grid. At higher load levels, comparable crack spacing developed in both the strengthening layer and the existing concrete section. Despite high carbon strains approaching the design strain limit, all crack widths remained well below the serviceability limit of 0.4 mm. In addition, a first analytical estimation of the cracking behavior was carried out based on simplified assumptions, which overall shows good agreement with the experimental results.