This study aims to link morphological and physico-chemical parameters with maturity stages of Natal plum (Carissa macrocarpa), an edible southern African fruit. Harvesting via an integrative holistic approach is recommended for optimal quality and functional compounds. Fruits at dark green (M1), light green (M2), colour break or pink (M3), red (M4), dark red (M5) stages were harvested in 2016 and 2017 seasons. The principal component analysis illustrated the colour value a* (redness), fruit weight, size (length and width), sugars (glucose and fructose), ascorbic acid content, cyanidin derivatives (cyanidin-3-O-pyranoside, cyanidin 3-O-β-sambubioside, cyanidin-3-O-glucoside), naringenin 4'-O-glucoside, and antioxidant property (FRAP) were higher in the following order of maturity stages M5 > M4 > M3 > M2 > M1. Quercetin 3-O-rhamnosyl galactoside and glucoside were higher in green (h° higher) firm M1 to M3 stages. A strong correlation exists between fruit weight, size, a* value and cyanidin derivatives or naringenin 4'-O-glucoside or ascorbic acid content or antioxidant activity. Thus, the M4 and M5 stages of Natal plum can serve as functional food.