The influence of central structure and side chain length on plasticizer effectiveness of succinate and maleate diesters blended into poly(vinyl chloride) (PVC) was assessed by tensile testing, DMTA, and surface hardness measurements. While no significant differences between central structures with similar side chain lengths were found, the length of the side chain played an important role, and maximum effectiveness was found for the linear dihexyl esters. In comparison to commercial plasticizers such as DEHP and Hexamoll® DINCH®, succinates and maleates with linear side chains of four to eight carbons performed as well or better in several of the mechanical tests. Earlier work had established that the proposed succinate and maleate compounds exhibited higher biodegradation rates than DEHP, and pending toxicity studies, they seem to be viable replacement compounds for DEHP.