Cross-Laminated Timber (CLT) shear-walls composed of multiple panels are nowadays a viable alternative to single-panel CLT walls in mid-rise construction sector. Prefabrication process, transport and erection limits are some of the reasons why short panels, vertically-jointed by means of mechanical fasteners, are preferred to CLT single-panel walls. When a significant amount of energy dissipation in the vertical joint is not required (i.e. low seismic prone areas), stiff vertical joints are preferred: the wall behaves mostly like a single-panel wall and vertical joints are designed to minimize the relative displacement between the panels. This paper presents an experimental campaign on aluminium stiff shear-key connector, as an alternative to traditional screwed connections for stiff vertical joints in multi-panels CLT walls. Monotonic tests were performed on shear-key connectors and full-scale tests on multi-panel CLT shear walls were carried out. A numerical model was developed in order to extend the experimental results on full-scale tests by means of a sensitivity analysis.