Two aluminum Schiff base catalysts with the formula LA1Et [L = bis(benzoylacetone)trimethylenediimine (1) or bis(benzoylacetone)ethylenediimine (2)] were designed and synthesized for a comparison of their catalytic properties in the polymerization of racemic lactides. Single-crystal data of catalyst 1 confirmed its trigonal bipyramidal configuration with a five-coordinated aluminum atom in the center. These catalysts were shown to be highly active and stereoselective for the controlled ring-opening polymerization of racemic lactides.