The objective of this study was to identify the association between knowledge about nutrition with the presence of obesity or overweight in women with low income in Mexico City. Data was obtained with the Urban Food and Nutrition Survey 2002 in the Metropolitan Area of Mexico City (ENURBAL 2002), a stratified multistage and clustered design survey. An ordinal logistic regression model was used in order to estimate the probability to present obesity and overweight or obesity, in relation to nutritional knowledge, age, education, employment, socioeconomic status, and total fat consumption. The variables that were related to overweight or obesity: correct or regular nutrition knowledge (OR = 2,00; CI95% = 1,13-3,54) and (OR = 1,54; CI 95%= 1,03-2,30), respectively; age 30 years (OR = 3,00; CI 95% = 1,94-4,64), belonging to a medium- low socioeconomic status (OR = 2,04; CI 95% = 1,33-3,15), and high fat consumption (OR = 1,65; CI 95% = 1,07-2,55). For obesity was age 30 years (OR = 2,42; IC 95% = 1,48-3,94) and high fat consumption (OR = 1,67; IC 95% = 1,05-2,66). Our results helped to identify associated factors in women with obesity and overweight from low income households, mainly those concerning with nutrition knowledge. This emphasizes the importance of improving knowledge about nutrition, in planning the strategy for interventions aimed to prevent overweight and obesity.