The Andean Tropics are among the mountain systems most affected by climate change. The most conspicuous effect is glacier recession. However, little is known about how rural populations perceive climatic change impacts or about how social-ecological systems respond to the effects of change. Here, I examine perceptions of climatic change and their effects on social-ecological systems in the Peruvian Southern Andes. Data from interviews and focus groups are used to explain institutional responses to climatic variability based upon perceived effects of climate change. Results show that people perceive glaciers shrinking, more frequent and intense extreme weather events, more extreme temperatures, and shortened rainy seasons. Their responses to these perceived changes range from wetland creation to agriculture calendar modification to irrigation adjustments. Such perceptions of change rely on personal observations and local knowledge, which inform responses; knowledge-based action characterizes resilient systems. This case study supports the conclusion that the resilience of social-ecological systems in the Peruvian Southern Andes is based upon local knowledge and institutions. Thus, strengthening institutions and fostering local knowledge renewal are crucial for systems' sustainability or transformation.