The aim of this work was to develop pH sensitive composite hydrogels based on Rhinobatos cemiculus gelatin (RCG) and reinforced with cellulose microcrystals (CM) for vitamin B2 controlled release. Hydrogels were synthesized using different CM ratios. The structure and stability of the prepared hydrogels were determined using FTIR, SEM, DSC and TGA analyses. The presence of CM effectively improved the mechanical properties, the resistance to thermal degradation, and the compactness of composite hydrogels, as evidenced by rheological and dynamic mechanical tests. Moreover, the pore size decreased and became more regular with the increase of CM content. Additionally, RCG hydrogels loaded with 5% of CM, in acidic medium, underwent higher swelling rate, compared to other hydrogels in neutral and basic media. Hydrogels’ porous microstructure and swelling behavior were determining parameters in riboflavin entrapment efficiency and controlled release rate. This supplied flexible choices for the development of drug carrier for controlled delivery.