Two main disadvantages of starch-based biofilms are their low mechanical strength and high hydrophobicity. This work investigated incorporation of cellulose microfibers (CMF) with a range of CMF loading (i.e., 0, 0.5, and 1.0 wt of CMF) as fillers to improve the mechanical properties of starch-based biofilm. CMFs (average diameter = 75 μm) were isolated from midrib of Musa Saba' banana residue using chemical treatments of steam explosion alkaline treatment, acid-chlorite treatment, and acid hydrolysis. The starch-based biofilm showed improved tensile strength (32.5), Young's Modulus (55.4), opacity (23.7), crystallinity (54.2), and reduction in elongation (27) with 1.0 wt CMF loading compared with biofilm without CMF. The film's mechanical properties improvement is further supported by the even filler dispersion within the film matrix shown in field emission scanning electron microscope micrographs. Active packaging containing the antimicrobial compound of myricetin was incorporated into the 1.0 wt CMF reinforced film to produce SC1M, which showed the fastest release of myricetin in 95 ethanol (fatty acid simulant), followed by 3 acetic acid (acidic simulant) and slowest in distilled water (aqueous simulant). CMF derived from banana midrib residue can be a viable bioreinforcement component for developing biofilms for fatty food packaging, which protects against humidity, oxygen, temperature, and light-induced deterioration. © 2023 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals LLC.