One of the key characteristics of fresh mortars is their rheological behaviour since it determines the material workability and has a clear influence on the hardened product final properties. Indeed, mortars rheological properties are extremely important since several factors, related with placement, consolidation, durability and strength depend on the flow properties of the mortar paste. In this work, the effect of ageing time on the rheological properties of fresh aerial lime-based mortars was investigated. Mortars having a 1/3 binder/aggregate volume ratio were studied as a function of ageing time. The influence of a water retaining agent (0.1 wt. %) addition in these mortars was also analysed. Mixing and ageing have a clear influence in the water intake process ruling over the rheological behaviour of this type of mortars.