Obesity is a chronic condition worldwide and has frequent association with major depression. The Montgomery-Åsberg Depression Rating Scale (MADRS) was applied to obese patients in order to detect briefly and systematically depressive symptoms. The objectives were: to estimate the reliability of the MADRS and to investigate the criterion validity of MADRS. The best cut-off point to detect depressive symptoms was determined in comparison with the Structured Clinical Interview for DSM-IV Axis I Diagnosis (SCID-I). The sample was recruited consecutively from the waiting list of a bariatric surgery service of the university clinic. Trained clinical psychologists applied the assessment instruments. The final sample was comprised of 374 class III obese adults (women 79.9 %, mean age 43.3 years [SD 11.6], mean body mass index 47.0 kg/m2 [SD 7.1]). The mean total score of the MADRS was 7.73 (SD 11.33) for the total sample, with a Cronbach’s alpha coefficient of .93. Women presented higher mean score than men (8.08 versus 6.33; p = .23). The best cut-off point was 13/14 in accordance with the Receiver Operating Characteristics (ROC) curve analysis, yielding a sensitivity of .81 and specificity of .85. The overall ability to discriminate depression according to area under the curve was .87. The results showed that the MADRS is a reliable and valid scale to detect depressive symptoms among patients seeking treatment in preoperative period, displaying adequate psychometric properties.