ABSTRACT Present study aims to develop Hall-Petch and Hollomon models for Al-6.2 wt.%Cu-0.6 wt.%Mg alloys microalloyed with varying Sn contents, under different thermo-mechanical treatments. Average grain sizes were microscopically determined, and uniaxial tensile tests were conducted to generate flow curves and evaluate yield strength of the alloys. Average grain diameter of Al-Cu-Mg base alloy decreased (by 19.9 %), while yield strength concomitantly increased (by 17.6 %), with increasing Sn content up to 0.06 wt.%. Rolled peak-aged alloys recorded highest average grain refinement and increase in yield strength by 41% and 98.8% respectively, among all thermo-mechanical treatments. Influence of grain size on mechanical strength was analytically modelled through Hall-Petch equation, using Weighted Least Square methodology. Hall-Petch parameters of the alloys were evaluated for first time, considering separate processing conditions. Yield strengths computed from Hall-Petch models were successfully compared with experimental results with fairly good accuracy, to validate estimated Hall-Petch parameters. Flow curves obtained from uniaxial tensile tests were mathematically modelled through Hollomon equation, by determining strain hardening exponent and strength coefficient, first time for investigated alloys under different processing conditions. Trace contents of Sn and processing parameters had significant potential to refine grain structure and enhance mechanical strength of the Al-Cu-Mg alloy.