GaSb quantum dots (QDs) have been grown by solid-source molecular beam epitaxy on a 4-monolayer (ML) InxGa1-xAs (x = 0.07, 0.15, 0.20, and 0.25) to investigate the effects of In-mole-fraction of InGaAs insertion layers on the structural and optical properties of the GaSb QDs. The density of grown GaSb QDs is approximately 1.2-2.8109 cm−2 on In-GaAs insertion layers which depends on the In-molefraction. Dot shape and size change substantially when In-mole-fraction of InGaAs insertion layers is varied. The uniformity of GaSb QDs improves when the indium content increases. The change in freestanding QD morphology is likely due to the modified strain at different values of indium compositions in InGaAs insertion layers. The effects of In-molefraction of InGaAs insertion layer on optical properties of the QDs are studied by photoluminescence (PL). PL results show the blueshift of the emission when the indium content in InGaAs insertion layer increases.