The effect of polyphenol fortification of red-fleshed plum nectars by addition of plum skin extract on the stability of quality, defined in terms of sensory attributes, phenolic composition and antioxidant activity, during shelf life storage was investigated. The sensory attributes were stable throughout the 3-month storage period at 5 °C for the control and fortified formulations. Among the phenolic compounds measured only the anthocyanins decreased during the storage period; however, the total antioxidant activity was not affected. The loss of red colour was less pronounced compared to the loss of anthocyanins for both formulations. This might be attributed to enhanced co-pigmentation as the content of the co-pigment, neochlorogenic acid, increased, while flavonols remained stable during storage. Polyphenol fortification enhanced the retention of red colour, polyphenol content and total antioxidant capacity compared to the control formulation.