Blends of poly(vinyl chloride) (PVC) and poly(butylene adipate) (PBA) with varying degrees of branching were analyzed with respect to migration resistance during aging in water, preservation of material properties, and thermal stability. Gas chromatography-mass spectrometry, water absorption, weight loss, thermogravimetric analysis, Fourier transform infrared spectroscopy, contact angle, tensile testing, and differential scanning calorimetry were used to analyze the blends before and after aging in water for 6 weeks. Films plasticized with slightly branched polyester maintained their material and mechanical properties best during aging. High degree of branching was accompanied by poor miscibility, increased hydrophilicity, and polydispersity, and highly branched PBA was not favorable as a plasticizer. Strong intermolecular interactions reduced the water absorption and increased the migration resistance of the blends. Polymeric plasticizers with no, low, or moderate degree of branching improved the thermal stability of films compared to films plasticized with a traditional phthalate plasticizer. Proper design of plasticizer architecture led, thus, to improved migration resistance, long-term properties, and thermal stability in PVC/polyester blends.