Lime-natural pozzolan based mortars are very common in historic buildings, as they provide adequate moisture removal from the masonry and are stronger and more durable than air lime mortars. Furthermore, lime-natural pozzolan mortars represent a more environmentally friendly option than lime or cement-based mortars. In some cases, animal fibers, especially goat and bovine, have been used in mortars in the past. When designing and developing mortars for the repair and restoration of historic buildings, compatibility requirements with historic mortars and masonry must be met. For this reason, The aim of this paper is to investigate the effect of the addition of horsehair, goat hair, bovine hair and pig hair on the physico-mechanical and microstructural properties of lime-pumice mortars. The investigated fibers were added to the mixture at 0.25%, 0.5% and 1.0% by weight of binder and compared with the untreated mortar. The addition of all animal fibers required a greater amount of mixing water to maintain the same flow rate of fresh mortar, which particularly affected the initial strength and porosity of the mortars. All mortars with fibers were more frost resistant than the reference mortar and significant changes also occurred in the capillary action of water through the mortars. Goat hair, in particular, appears to be very promising for improving not only the physical and mechanical properties of lime-pozzolan mortars, but also the transport of water from damp masonry and the durability of mortars.