This work evaluated the influence of compressive strength and confinement on the stress-strain behavior of axial loaded mortar specimens by means of experimental and numerical analyses. Two mortars were tested, with volume proportions of cement, lime and sand of 1:0.5:4 and 1:1:6. Two specimen heights, 50 and 140 mm, with diameter of 45 mm, resulting in diameter/height ratios of 1.0 and 0.3, respectively were used. The experimental results indicated that the confinement and strength of the mortar influence its stress-strain behavior: the larger the confinement, the more the non-linear behavior. In addition, the results indicated that the Poisson’s ratio and the tangent modulus of elasticity vary with increasing applied load. A numerical model was developed that accounted for the observations from the experimental phase with a nonlinear elastic phased analysis, which updates the modulus of elasticity and the Poisson’s ratio at each new phase. The tangent modulus of elasticity was calculated directly from the experimental results while the Poisson’s ratio was approximated using the model proposed by Ottosen. The numerical model presented satisfactory results, even close to the failure, when cracking is significant.