Fruit growers are looking for effective solutions to maintain apple quality after long-term storage. Therefore, the aim of this study was to evaluate the effect of pre- and post-harvest application of 1-MCP on the quality of "Gala Schniga® SchniCo Red(s)" apples harvested at two different harvest dates and stored for 7 months under DCA conditions (0.6% CO2 and 0.6% O2) at a temperature of 1°C and a relative humidity of about 95%. The study was conducted during the 2022/2023 storage season on apples harvested at both the optimum (September 13, 2022) and delayed (September 26, 2022) harvest dates in four combinations: control - no application of 1-MCP both before and after harvest; Harvista™ (containing 1-MCP; 150 g/ha) - trees sprayed 7 days before the optimum harvest date; SmartFresh™ - fruit treated with 1-MCP at a concentration of 0. 65 µL/L 7 days after harvest; Harvista™ + SmartFresh™ - fruit treated with 1-MCP 7 days before optimum harvest date and 7 days after harvest (in storage). Immediately after 5 and 7 months of storage and after an additional 7 days at 20°C (simulating wholesale and retail conditions), the following were determined: flesh firmness, soluble solids content, titratable acidity, ethylene production rate and analysis of the ethylene synthesis precursor ACC (1-aminocyclopropane-1-carboxylic acid), and measurements of respiration rate intensity. The intensity of ethylene production depended on the time of harvest and the time of treatment with the compound 1-MCP, as reflected in the retention of firmness and titratable acidity, respectively, after storage (p < 0.05). Apples harvested at the optimum time from trees sprayed with Harvista™ retained high firmness (>55 N) after 7 days of rotation at 20°C, even after 7 months of storage. In contrast, when apples were harvested at a later time, only fruit treated with 1-MCP after harvest exhibited firmness close to that characteristic of the best eating maturity. In addition, the intensity of ethylene production was found to be related to the change in ACC content of the fruit. Therefore, it seems that the application of 1-MCP leads to a general reduction and/or inhibition of parameters related to ethylene synthesis. At the same time, post-harvest application of 1-MCP significantly slows down fruit respiration even after 7 months of storage under DCA conditions.