This study assesses the sustainability of urban and peri-urban agriculture (U&PUA) in the Quito canton from environmental, social, and economic perspectives, using the MESMIS methodological framework. Based on a survey conducted with 66 producers, key indicators were analyzed, including crop diversity, the use of agroecological practices, water resource management, community participation, and the economic contribution of U&PUA to households. The findings reveal a high level of productive diversification and widespread adoption of organic inputs and biofertilizers, alongside the use of efficient irrigation systems and rainwater harvesting. These practices strengthen food security and reduce dependence on synthetic inputs, positioning U&PUA as a low-impact strategy for sustainable food production in urban contexts. Socially, the study highlights strong participation of women and older adults, who lead community processes, reinforce social cohesion, and preserve agroecological knowledge. Economically, U&PUA supports household food self-sufficiency, although its contribution to income remains limited due to market access barriers and insufficient institutional support. The integrated assessment yielded a sustainability score of 2.56 out of 5, indicating a moderate level of sustainability, with strengths in food security and biodiversity, but also highlighting critical challenges in social equity and economic viability. It is concluded that U&PUA represents a strategic tool for building more climate-resilient cities and enabling a just transition toward sustainable agri-food systems. Practical implications include the need to strengthen municipal support for urban agriculture policies, incorporate U&PUA into land use and food planning frameworks, and facilitate access to technical training, financing, and inclusive markets.