An experimental investigation into the shear transfer across the brick mortar interface at different levels of applied pre-compression is reported. Direct shear tests are performed in the triplet test configuration on masonry made with a soft brick. The failure across the brick–mortar interface is progressive and is produced by a crack in the brick–mortar interface. The interface crack propagates in a thin layer where the mortar penetrates the brick. A cohesive-frictional interface relationship which combines progressive cohesive failure with increasing frictional resistance is developed. The maximum shear resistance obtained from the cohesive-frictional relationship follows a Mohr–Coulomb type relationship. The residual frictional resistance increases linearly with an increase in the applied compression. © 2019, RILEM.