This study aims at assessing the effect of solution heat treatment (at a temperature just below the eutectic temperature) followed by various cooling rates on the microstructure and mechanical properties of additively manufactured AlSi10Mg and the cast counterpart. The mechanical properties were evaluated using a depth-sensing nanoindentation platform. The cast and additively manufactured parts were solutionized at 540 ​°C for 2 ​h followed by water quenching, air cooling, and furnace cooling. Results show extensive microstructural changes (e.g. size and morphology of eutectic-silicon phase) and evolutions in the mechanical properties of the heat-treated materials relative to the as-printed and as-cast ones. Besides, the microstructure and micromechanical properties of the materials broadly alter the cast and additive manufacturing conditions. Depending on the cooling condition, the mentioned cooling cycles directly affect the morphology of eutectic-silicon in both cast and additive manufactured materials starting with silicon fragmentation, then followed by silicon spheroidization, and silicon coarsening. The microstructural evolution affects the local micromechanical properties of the studied materials. The results of this study provide insights into the control of microstructure and hence mechanical properties of AlSi10Mg alloy by addressing suitable heat treatment cycles. This study, for the first time, assesses and compares the effect of various post-fabrication cooling rates in the cast and additive manufacturing conditions in an AlSi10Mg alloy.