Because of the growing need for more sustainable materials, the production of bio-based and biodegradable plastic products has been rapidly increasing in recent years. These materials can be used in a variety of applications, the majority of which are in the packaging industry. In this research blend of polylactic acide (PLA) with polyethylene terephthalate (PET) was prepared. The surface tension measurements were used to estimate interfacial tension values between the two blend components and the findings showed good adhesion between the two components. Morphology was investigated through scanning electron microscopy (SEM) and the results showed PET and PLA was immiscible, but compatible with each other, characteristics also reflected in the microstructure. FTIR studies illustrated the PLA structure in the PET matrix. Interactions were analyzed by 1H NMR and the exchange reaction was confirmed. DSC results showed shifting in glass transition temperatures (Tg) that indicate interactions between these materials. Because of formed copolymers through transesterification, the crystallization process in the film became difficult as the PLA was added to the PET matrix. Presence of PET crystals in the blend film was confirmed by X-ray scattering patterns.