The synthesis of Al nanocrystals (Al NCs) is a rapidly expanding field, but there are few strategies for size and morphology control. Here we introduce a dual catalyst approach for the synthesis of Al NCs to control both NC size and shape. By using one catalyst that nucleates growth more rapidly than a second catalyst whose ligands affect NC morphology during growth, one can obtain both size and shape control of the resulting Al NCs. The combination of the two catalysts (1) titanium isopropoxide (TIP), for rapid nucleation, and (2) Tebbe’s reagent, for specific facet-promoting growth, yields {100}-faceted Al NCs with tunable diameters between 35 and 65 nm. This dual-catalyst strategy could dramatically expand the possible outcomes for Al NC growth, opening the door to new controlled morphologies and a deeper understanding of earth-abundant plasmonic nanocrystal synthesis.