Multi-layer biaxially oriented compostable composite film with a sealant layer formulation has improved heat seal initiation temperature, enhanced plateau seal strength, and broadened heat seal temperature range, while optical clarity is maintained, and film modulus (noise) is reduced. The film includes a core layer comprising a PLA-rich biodegradable composite resin, and a heat sealable layer comprising 20 to 60 wt % amorphous polylactic acid resin, and 40 to 80 wt % flexible compostable polymeric modifier Y having a glass transition temperature of Tg≤0° C. and a melting temperature of 56° C.≤Tm≤90° C. Specifically, the flexible compostable polymeric modifier includes 20 to 70 wt % polybutylene succinate-co-adipate (PBSA) copolymer and 5 to 35 wt % polycaprolactone as a promoter of low heat seal initiation temperature (SIT) and hermeticity. The inventive compostable composite film is desirable to have improved home compostability.