Aim: To study the adiponectin levels during puberty in girls with type 1 diabetes mellitus (DM1) and their relationship to body mass index (BMI), Tanner stage, ovarian volume (OV), and androgen levels. Methods: We studied adiponectin and testosterone levels and OV in 56 pubertal girls with DM1 and in 59 healthy girls serving as controls. The effects of DM1, BMI standard deviation scores (BMI SDS), testosterone, and OV over adiponectin levels were assessed. Results: The adiponectin levels were higher in the DM1 girls as compared with the controls. There was a significant decrease in adiponectin concentrations during puberty in DM1 girls only. The adiponectin levels in the girls with DM1, but not in the controls, exhibited a negative correlation with OV (r = –0.427, p = 0.002) and testosterone (r = –0.262, p = 0.049). Regression analysis showed DM1, BMI SDS, testosterone levels, and OV to be significant factors over adiponectin levels. The effect of Tanner stage was due to differences in BMI SDS. Conclusions: Decreasing adiponectin levels observed during puberty in adolescents with DM1 correlate with increasing testosterone levels and OV. We observed higher adiponectin levels in DM1 patients only at the beginning of puberty. The lack of elevated adiponectin levels observed during the late stages of puberty in girls with DM1 may be involved in the metabolic abnormalities observed during this stage.