Under extreme dynamic loads, such as collisions and blasts, materials exhibit enhancements in most of their mechanical properties due to the high rate of loading. Air lime is an extensively used binder in historical masonry structures, and it is currently incorporated in their repair. Understanding the behaviour of air lime mortars under high strain rates is particularly important for the assessment of historical structures. In this context, this study examines the dynamic compressive properties of a rich lime-putty mortar mix with a 1:1 lime-putty-to-aggregate ratio at ages exceeding 9.5 months. A series of impact tests were carried out on 50 mm size cube specimens under different impact velocities. Peak strain rates of more than 40 s−1 under the impact of 7.0 kg mass at velocity of 7.3 m/s were achieved. The dynamic impact results were compared against their quasi-static counterparts to evaluate the sensitivity of the mortar’s mechanical properties to different strain rates. Compressive strengths and ultimate strains are presented in this study. A three-dimensional digital image correlation technique, using two high-speed cameras, was used during the dynamic testing to measure surface strains and their corresponding strain rates over two surfaces of the cubes. Both compressive strengths and ultimate strains showed sensitivity to strain rates of more than 2 s−1 and 8 s−1, respectively.