Milk technological and physicochemical characteristics are vital to cheese yield and quality, but can vary in response to factors such as season. An evaluation was done of milk technological and physicochemical characteristics in the dry and rainy seasons, and their effects on the physicochemical characteristics of traditional Oaxaca cheese. Milk and cheese samples were collected from 21 different small-scale processing plants. Milk samples were analyzed for fat and protein content, acidity level, coagulation time, curd firmness and yield. Cheese samples were analyzed for fat and protein content, acidity level, moisture content and chlorides level. A one-way ANOVA was used to evaluate inter-seasonal changes. Differences by season were observed in milk fat and protein contents, acidity level, coagulation time, curd firmness and yield. In the cheese interseasonal differences were present in fat content, acidity level and moisture content. Season clearly affected milk physicochemical and technological characteristics, and consequently cheese composition.