•An investigation of the behaviour of CLT shearwalls with openings is undertaken.•Failure modes related to either mechanical anchor or CLT panel are studied.•Full-scale shearwall tests were used to validate a proposed numerical model.•Input parameters for numerical model were obtained from component level tests. An investigation of the mechanical behaviour of CLT shearwalls, where either door or window openings are cut out of the panel, is undertaken. The main aim of the study is to investigate failure modes related to either mechanical anchor or CLT panel, based on the geometrical dimensions and mechanical properties of shearwall. The results of six full-scale monolithic CLT shearwalls with window or door openings are presented and discussed. The results obtained from the full-scale shearwall tests are used to validate a proposed numerical model, where input parameters, such as the mechanical properties of the CLT panels and mechanical anchors, are obtained from component level tests on beams and connections in isolation. The study shows that differently from single-panel shearwalls with no openings, brittle failure in the CLT panels is a possible mode of failure, which needs to be considered in design. The failure mode in the CLT panels is observed to occur either in bending or net shear in the lintel beams. The proposed numerical procedure is found capable of estimating the maximum load with reasonable accuracy, and the model predictions of the failure mode, number of centre of rotations, and the overall deformation of the CLT panel are accurate for all the studied specimens.