This study sought to use the stress–strain relationship of interlocking stabilized soil block (ISSB) masonry to model its behaviour and develop empirical formulae to aid in predicting its compressive strength. A finite element (FE) analysis adopting the Rankine failure criterion was performed using Abaqus software to simulate the deformability behaviour of the wall which was validated through experimental tests. The compressive strength, modulus of elasticity and density of ISSB defined in the FE model were determined by performing laboratory tests on laterite soil blocks stabilized with pozzolanic cement, hydrated lime and rice husk ash. Conversely, the predictive empirical formulae for the compressive strength of the ISSB masonry was developed by performing statistical multiple regression analysis. In addition to the mechanical properties of masonry, the FE simulation results indicated that the deformability behaviour of ISSB masonry is influenced by the type of stabilizer used on the target material. This dictated the stress distribution and vertical displacement on the masonry. A diagonally stepped failure mode was experienced in more brittle masonry while cone failure mode was observed in less brittle masonry assemblage.