Inspections of defective masonry bridges and viaducts still in service have indicated that repeated loading due to heavy traffic may accelerate the deterioration of masonry materials, potentially leading to reduced performance. These observations have highlighted the need to account for fatigue effects when evaluating the serviceability and ultimate behaviour of masonry arch bridges. Previous high-cycle fatigue tests on stocky columns under compression corroborated that the fatigue strength is approximately 50% of the static strength for brick masonry. However, there is a lack of experimental evidence about the potential deterioration of the bond and shear strengths of mortar joints in masonry arches under high-cycle loading, which may affect the actual fatigue response of masonry bridges. This paper presents and discusses the results of physical experiments on brick-masonry arch specimens. Digital image correlation is used to capture the evolution of displacements and crack widths, shedding light on the degradation of mortar joints under shear and bending stresses induced by high-cycle fatigue loading.