This aricle aims at investigating for the first time the ability of using poly(3-hydroxylbutyrate-co-3-hydroxyvalerate) (PHBV)/wheat straw fibers (WSF) biocomposites as food contact materials for packaging applications. For that purpose, the impact of the filler size and content on overall migration and mechanical properties was assessed under standardized testing conditions using the food simulant liquids (FSL). Very high overall migration values were noticed in the case of hydrophilic FSL, that is, water, acetic acid 3% (wt/vol), ethanol 20% (vol/vol), and ethanol 95% (vol/vol), related to the leaching of water extractable components of WSF. Low migration values were obtained in contact with isooctane and olive oil, demonstrating the possibility of using biocomposites in contact with fatty products. To answer the lack of methodologies to simulate different types of food for which PHBV-based composites could be more specifically dedicated, including food products of low or intermediate water activity such as fruits and vegetable, bread, and cheese, a new range of new solid food models based on agar-agar gels have been developed. Results showed that the water activity (a(w)) was the main parameter governing the overall migration of PHBV/WSF materials, suggesting that such composite materials could only be used as food contact materials in the case of food products with an a(w)equal or lower than 0.90.