The agri-food industry generates tons of waste rich in dietary fiber, a nutrient that can be recovered to be reused in the development of fiber-enriched foods and beverages. This could be a strategy to achieve resource-use efficiency and to promote adequate intakes of this nutrient, since a large part of the world population does not get the recommended daily amount. In this sense, this work was carried out to optimize the extraction of dietary fiber from quince (Cydonia oblonga Mill.) peel using the response surface methodology. A 20-run experimental design was implemented, combining the independent variables time, temperature, and ethanol percentage at five levels. In addition to the extraction yield (w/w), the dietary fiber content and color parameters of each fiber extract were used as response criteria. The developed predictive models were statistically validated and used to determine optimal extraction conditions. In general, the extracts with higher yields tended to contain lower percentages of dietary fiber, and those containing more fiber were darker. The process was significantly affected by the temperature and ethanol percentage used in the extraction and the highest fiber content (67% of the extract) was obtained using 92 ºC and 36% ethanol. Overall, this study showed that quince peel can be upcycled into dietary fiber concentrates, which could be exploited as food fortifiers.