<p>The global transition toward sustainable packaging is often hindered by the low extraction efficiency and limited functional performance of plant-derived colourants when incorporated into biopolymer films. Therefore, this study investigated the extraction of bioactive compounds from red spinach (<i>Amaranthus dubius</i>) and evaluated their potential application in starch-based packaging films through transparency and water vapour permeability. Red spinach extracts were obtained using various chemical solvents (ethanol, methanol, acetic acid, and distilled water) at different concentrations, as well as through an integrated chemical–ultrasound-assisted extraction (UAE) approach. The results demonstrated that the integrated chemical–UAE method improved extraction performance compared with conventional chemical extraction. Under methanol-based conditions, the UAE-assisted extraction achieved the highest extraction yield of 13.96%, which was substantially higher than that obtained using conventional methanol extraction (6.53%). Although ultrasound-assisted extraction using distilled water may influence the stability of heat- and cavitation-sensitive pigments such as betacyanins, the process enhanced cell wall disruption and promoted the release of bioactive compounds, resulting in high antioxidant activity (98.93% DPPH radical-scavenging activity). This red spinach extract obtained from integrated water-UAE assisted extraction was then implemented into starch film resulting in increased film opacity, improved light barrier properties, and reduced water vapour permeability during storage compared with the control film. These improvements may contribute to better protection of packaged foods against moisture transfer and light-induced deterioration. These findings suggest that <i>Amaranthus dubius</i> can act as a potential candidate for active packaging applications aimed at enhancing food shelf-life and preserving the food quality.</p> Graphical Abstract <p></p>