Natural hydraulic and aerial lime mortars are used extensively for restoration works due to their good compatibility with the substrate material in historical masonry construction. Recently, the study of the influence of loading rate of such materials is getting more attention due to the fact that many historic masonry structures are situated in zones of seismic activity. However, the references are still scarce in comparison to that of steel and concrete and the studies focused on the measurement of the influence of loading rate on the fracture energy are limited, although it is an important parameter to characterize the ductility and the fracture behaviour of the material. Thus, in the paper, an aerial and a natural hydraulic lime mortar specimens were tested at various loading rates (loading-point displacement rates) from the quasi-static one, 5.0 × 10 -4 mm/s, to rate sensitive ones, 5.0 × 10 -1 mm/s and 1.6 × 10 1 mm/s. For this purpose, it was used a servo-hydraulic testing machine up to its maximum range of velocities. The results show that the fracture energy and the peak load of both lime mortars are rate sensitive. The maximum dynamic increase factors of the fracture energy are 1.9 for both mortars, while 1.4 and 1.6 for the natural hydraulic and the aerial lime mortars, respectively, in the peak load. This behaviour is related to viscous effects of free water in the mortar.