Masonry shear walls serve as essential lateral load-resisting members in many structures. The shear strength of masonry walls is a critical material property, typically assessed through the European triplet test (EN 1052:3–2002) or ASTM E519’s diagonal tensile shear test. However, the ASTM procedure is difficult to conduct in practice, and the triplet test results available in the literature predominantly focus on clay bricks, with few data on hollow concrete blocks. Additionally, the absolute shear strength is hard to quantify due to the flexural stresses associated with common shear tests. In this study, the behavior and strength of masonry triplets constructed with Canadian concrete masonry units subjected to shear load were investigated. The specimens varied between non-grouted, partially grouted, and fully grouted. The triplets were subject to various precompression levels, ranging from 0 to 3 MPa. Specimens were loaded monotonically until failure and strains across the specimens were monitored. The test results were utilized to quantify the contributions of the flexural, cohesive, and frictional components to the strength of triplets. The results demonstrated that both grout and precompression levels significantly enhance the shear strength of concrete masonry.