Every year millions of tons of non-degradable plastic waste are originated all over the world. Because of the serious environmental problems associated with this situation, there is a great worldwide interest in replacing fossil fuel-based plastics with natural and biodegradable polymers. In this work we present a simple and direct method to produce bioplastics from seaweed residues without the need for extracting or purifying the different components present naturally such as cellulose, alginic acid and others. Specifically, we report the preparation of bioplastics from red algae (Porphyra yezoensis) residues blended with cellulose using trifluoroacetic acid as common solvent. Bioplastics films were obtained by casting solutions of dried and pulverized seaweed residues and microcrystalline cellulose. The chemical, morphological and structural characterization of such films showed that the samples are composed by a polysaccharide and amorphous matrix with embedded microcrystalline structures. Mechanical and hydrodynamic properties were also investigated. Measurements indicated that the films with lowest concentrations of cellulose present low values of Young’s modulus compared to amorphous cellulose and a percent elongation of more than 50%. Moreover, biodegradation tests are being carried out and the initial results indicated the films degrade completely in seawater.