Spherical curcumin/polyvinylpyrrolidone nanocapsules (CurNC) with the improved water solubility and thermal stability than native curcumin (Cur) were synthesized. Subsequently, soy protein isolate-based pH-sensitive multifunctional packaging films reinforced with cellulose nanocrystals (CNC), CurNC, CNC/CurNC, and CNC/Cur were developed for shrimp freshness detection. It was found that adding the CNC-containing agents improved the tensile strength, hydrogen bond interactions, thermal stability, and crystalline structure of the film and decreased its water solubility and water vapor and oxygen permeability. The Cur-containing agents decreased the L* (lightness/darkness) and a* (redness/greenness) values and increased the b* (yellowness/blueness) and ΔE (total color difference) values of the film. A more dense and uniform matrix of the nanocomposite films was likely responsible for delaying the release of Cur from the film matrix. Interestingly, CNC/CurNC film displayed higher antiradical scavenging activity than CNC/Cur film, as well as remarkable color responsiveness to pH changes and NH3 presence. Moreover, the CNC/CurNC film was able to decrease the total volatile basic nitrogen of stored shrimp and visually monitor shrimp freshness in real-time.