Blends of starch with polyesters have commonly been used in the production of biodegradable films. However, the components in the blend are not always miscible; therefore, the use of compatibilisers is recommended. The objective of the present work was to study the compatibilisation effect of adipic acid (0.5%; 1.0%; 1.5% (w/w)) on films consisting of starch/glycerol/poly (butylene adipate-co-terephthalate) (PBAT) produced by reactive extrusion. Films compatibilised with adipic acid exhibited statistically significant increase in tensile strength (from 7.28 to 8.45–9.13 MPa), elongation (in this case only with 0.5% of adipic acid) (516.51–679.10%), Young's modulus (21.72–28.75 MPa) and reduction in water vapour permeability (9.76–8.32 × 10−11 g per s.m.Pa) compared with the control film, which lacked the compatibiliser. Films produced using the compatibiliser also presented a microstructure with fewer cracks. There were no differences in the thermal degradation and crystallinity profile of the films.