Abstract BACKGROUND Climate change has driven the expansion of viticulture in high‐altitude tropical regions. The dynamics of grape ripening and its metabolic profile are influenced by climatic conditions. This study aimed to identify the optimal harvest period for Cabernet Sauvignon grapes cultivated in an emerging Brazilian high‐altitude region using a targeted metabolomics approach. Phenolic composition, antioxidant activity, and physicochemical parameters were monitored over a 10‐week ripening period from veraison. RESULTS Grapes harvested between weeks 6 and 9 exhibited physicochemical attributes favorable to winemaking, including pH (3.50–3.63), soluble solids (21.33–21.43 °Brix), skin hardness (4.52–6.23 kg m s−2), berry firmness (157.83–177.62 kg m s−2), and color. Grapes from 6 and 7 weeks presented the highest levels of anthocyanins (delphinidin‐3‐glucoside, cyanidin‐3‐glucoside, petunidin‐3‐glucoside, malvidin‐3‐glucoside, among others), flavan‐3‐ols (epicatechin and epicatechin gallate), and flavonols (myricetin‐3‐O‐glucuronide, myricetin‐3‐O‐glucoside, and kaempferol‐3‐O‐glucoside). These metabolites contribute to color enhancement and stability through copigmentation, accounting for the elevated antioxidant activity observed at these stages. CONCLUSION Therefore, weeks 6 and 7 represent the ideal harvest period for Cabernet Sauvignon grapes in this high‐altitude tropical region, combining favorable physicochemical maturity with maximal phenolic content and antioxidant potential. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.