Red-fleshed pitaya is an attractive fruit not due only to the color of its flesh and skin, but also the scaly shape of its skin. In addition to being a source of vitamins and minerals, it has high commercial value and represents an alternative for cultivation in semiarid regions. Information about the post-harvest physiology of pitaya, which interferes with its ripening, allows the adoption of preservation and quality-maintenance practices. This study examines the respiratory activity and post harvest alterations of pitaya picked in the commercially immature stage of ripeness, by comparing them with fruits picked fully ripe. Physical and chemical aspects of the fruits were evaluated in two harvests, in 2019 and 2020. Six days after harvest, there was an increase in respiratory activity and a change in color in both ripe and commercially immature fruits. Therefore, pitayas picked commercially immature in both harvests had an increase in respiratory activity post-harvest, with a change in skin color during storage; and six days after harvest, in the 2019 harvest, the fruits resembled those that ripened on the plant, without having their quality compromised. However, in the 2020 harvest, six days after harvest, the fruits picked fully ripe showed soluble solids/titratable acidity ratio, betacyanins and ascorbic acid contents similar to those measured in the commercially immature fruits.