Obesity in Mexico has reached epidemic proportions; and body image and body satisfaction might be culturally related. Body dissatisfaction has been related to low self-esteem. The aim of this study was to assess the range of perception among Mexican teachers and parents of the ideal body size of adults, boys and girls. Two-hundred and five teachers and eighty parents from Tijuana and Tecate schools participated in the study. Participants were asked to indicate the ideal body size for each group, as well as their own ideal body size. Average perception of ideal body weight for adults 35 to 45 years of age was 4.0 ± 0.84. Average perception for boys and girls was 4.6. Positive correlations were shown between self-perception of body size and body mass index (0.62, P < 001), waist circumference (0.55, P < 0.001). Self-perception of body size was associated with perception of ideal body size for boys (0.23, P 0.001) and girls (0.22, P < 0.001), but BMI was not associated to perception of ideal body size for boys and girls. These results suggest that teachers and parents should be taught to more accurately assess excess weight status and to initiate action to prevent or correct excessive weight among children and adults.