Encapsulation is a valuable strategy to protect and deliver anthocyanins (ACNs), phenolic com-pounds with outstanding antioxidant capacity but limited stability. In this study, coacervation was used to encapsulate an ACNs-rich red cabbage extract (RCE). Two agri-food by-products polymers, whey protein isolate (WPI) and apple high-methoxyl pectin (HMP), were blended at pH 4.0 in a specific ratio to induce the formation of nanoparticles (NPs). The process optimisation yielded a monodispersed population (PDI < 0.200) of negatively charged (-17 mV) NPs with an average diameter of 380 nm. RCE concentration influenced size, charge, and antioxidant capacity in a dose-dependent manner. NPs were also sensitive to pH increase from 4 to 7, showing a progressive breakdown. The encapsulation efficiency was 30%, with a retention of ACNs within the polymeric matrix being influenced by their chemical structure: diacylated and/or C3-triglucoside forms were more efficiently encapsulated than monoacylated C3-diglucosides. In conclusion, we report a promising, simple, and sustainable method to produce monodispersed NPs for ACNs encapsu-lation and delivery. Evidence of differential binding of ACNs to NPs, dependent on specific ac-ylation/glycosylation patterns, indicate that care must be taken in the choice of the appropriate NPs formulation for the encapsulation of phenolic compounds.