In our previous study, a novel alginate-based bilayer film for slow-release wound dressings was successfully developed. We found that alginate alone yielded poor films; however, the addition of gelatine had significantly enhanced the drug dispersion as well as the physical properties. Here, an investigation of the drug–polymer interactions in the bilayer films was carried out. Drug content uniformity test and microscopy observation revealed that the addition of gelatine generated bilayer films with a homogenous drug distribution within the matrix. The FTIR and XRD data showed an increase in film crystallinity which might infer the presence of drug–polymer crystalline microaggregates in the films. DSC confirmed the drug–polymer interaction and indicated that the gelatine has no effect on the thermal behaviour of the microaggregates, suggesting the compatibility of the drug and excipients in the bilayer films. In conclusion, the addition of gelatine can promote homogenous dispersion of hydrophobic drugs in alginate films possibly through the formation of crystalline microaggregates.