Body image is a fundamental factor that influences a person's self-image throughout life and at all stages of life. Self-perception of body image and body mass index may be related, as the way a person views him or herself can influence their eating behavior and level of physical activity, which in turn can affect their weight and BMI. The aim of this study is to find the association between body mass index, age, and body self-perception of university students, analyzing possible differences according to the gender of the students. In total, 312 students answered five sociodemographic questions in addition to the Multidimensional Body Self Relations Questionnaire, which consists of 45 questions grouped into four dimensions. Spearman's Rho test was used to analyze the association between each of the Multidimensional Body Self Relations Questionnaire (MBSRQ) factors and body mass index (BMI). Statistical differences were found in dimension 3 (p < 0.01) of the MBSRQ questionnaire with respect to BMI in both sexes, and in dimension 1 (p < 0.01), a significant difference was found in female students. With the male gender, significant differences were found between age and BMI (0.04). Consequently, the sex to which the student belongs conditions his or her BMI with the self-perceived body image, so lines of action should be developed to improve self-image.