This thesis aims to aid in the development of biodegradable plastic blends utilizing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). PHBV is a bacterial polyester capable of biodegrading in all environments but requires blending with tough polymers for improved mechanical performance. PHBV and poly(butylene adipate-co-terephthalate) (PBAT) were found to be immiscible, however, through various changes in morphology at different blending ratios, the mechanical performance of PHBV improved. To encourage miscibility, two processing additives were utilized in an attempt to compatibilize PHBV and PBAT. This resulted in a stronger polymer blend, with a slight decrease in elongation at break percentage due to the crosslinking between the polymers. The marine degradation of PHBV80%/polycaprolactone (PCL)20% blends was tested in accordance with ASTM D7991-15. PHBV, PCL, and PHBV80/PCL20 were able to degrade 60%, 38%, and 45%, respectively, after 505 days, but the blends crosslinked by processing additives were unable to marine biodegrade under the testing conditions.