Because　petroleum-based　packaging　films　have　raised　increasing　concerns　associated　with　their　non-degradability,　there　has　been　growing　interest　in　developing　sustainable　and　biodegradable　films.　This　work　addresses　development　of　natural　polysaccharide　films　with　enhanced　mechanical　strength　through　synergistic　interactions　between　calcium　alginate　and　carrageenan.　The　maximal　tensile　strength　was　reached　with　a　value　of　19.1 MPa,　which　is　comparable　to　conventional　polyethylene　films.　At　the　meantime,　the　composite　film　demonstrated　a　matrix　of　properties　suitable　for　general　packaging　application　such　as　negligible　solubility　in　water,　high　thermal　stability　and　transparency.　Scanning　electron　microscopic　images　revealed　that　the　film　had　alginate　arranged　at　the　outside　surface　because　the　alginate　is　more　hydrophilic　than　carrageenan.　The　overall　structure　of　the　film　is　a　basic　one-phase　microstructure.　IR　spectra　confirmed　composite　formation.　These　results　demonstrate　successful　preparation　of　a　sustainable　and　natural　film　as　a　biodegradable　alternative　to　conventional　polyethylene　films　for　application　in　packaging.　©　2017,　Springer-Verlag　Berlin　Heidelberg.