Al-Sc-Zr alloy contains precipitate Al(Sc,Zr) shows good coarsening resistance due to the small diffusivities of Sc and Zr. Two supersaturated Al-0.4Sc-0.4Zr at% alloys were produced using melt-spinning and following extrusion. The coarsening behavior of supersaturated Al-0.4Sc-0.4Zr at% alloys was investigated using scanning transmission electron microscopy (STEM). Accelerated coarsening was observed in the extruded melt-spun ribbon with larger precipitate size and higher precipitate volume fraction than in melt-spun ribbon. The accelerated effective diffusivity after extrusion was explicitly linked to the initially refined extruded microstructure. Precipitate volume fraction and chemical composition in both melt-spun ribbon and extruded rod during annealing were quantified with the help of STEM and energy-dispersive x-ray spectroscopy. Precipitate size and number density were predicted using Umantsev-Olson-Kuehman-Voorhees model for ternary alloys, and the predictions showed good agreement with experimental results by considering changes in diffusivity and precipitate volume fraction.