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We aimed to prepare a new pH-sensing film based on the immobilization of purple cabbage anthocyanins (PCA) into Polyvinyl alcohol (PVA) reinforced by cellulose nanocrystals (CNC). FT-IR, XRD and TGA were used to assess the intermolecular interactions and thermo-stability of films. The addition of CNC and PCA resulted in an enhancement in UV–vis barrier, mechanical properties and moisture resistance. Inclusion of PCA imparted intelligent properties to the films. PCA-loaded films displayed strong visually detectable colorimetric responses to pH (2−13) and volatile ammonia. When applied to monitor shrimp freshness at 4 °C, PVA/CNC films containing 0.6 % PCA exhibited conspicuous color fluctuations from purple to gray blue upon deterioration. As a result, PVA/CNC-PCA colorimetric films were considered as intelligent packaging labels with significant mechanical, water vapor barrier properties and pH-sensing qualities for visual quality evaluation of fresh seafood products. [Display omitted] • Versatile PVA/CNC-PCA intelligent films are fabricated successfully. • Good compatibility and strong interactions are observed among PVA, CNCs and PCA. • PCA film produce naked-eye detectable colorimetric response to pH and ammonia gas. • PVA/CNC-PCA III film display sensitive color response to shrimp spoilage. [ABSTRACT FROM AUTHOR]