The work aimed to prepare functional biocomposites. Selected terpenes: pinene, limonene, or their mixture effectively modified montmorillonite clay used as a filler. XRD confirmed the intercalation of the modifier in the filler gallery. Moreover, the application of natural-based modifiers caused changes in the structure of composites in the interfacial polymer-filler interactions. This allowed for the improvement of the strength properties of composites compared to unmodified PBS. Introducing the filler into PBS slightly increased tensile strength, but the barrier properties towards gases (oxygen and water vapor) were significantly improved. WVTR values for composites were almost twice as low as those for pure PBS film. FTIR, XRD, and DMTA analysis revealed that the introduction of the additive did not significantly affect the morphology, and the filler remained intercalated and well dispersed in the matrix (SEM results).