Background: Using the Mood and Feelings Questionnaire (MFQ) to differentiate between depression severity levels remains unexplored. We assessed the discriminative validity of the MFQ to identify an optimal cut-off MFQ score to distinguish between subthreshold-to-mild and moderate-to-severe depression severity levels. Methods: An observational cross-sectional design was used in a sample (N=67) of help-seeking youth (ages 13 to 18, inclusive) experiencing depressive symptoms. The MFQ was administered verbatim to youth by a research analyst over the phone. Youth were then grouped into subthreshold-to-mild or moderate-to-severe depression severity categories based on scores received on the Kiddie Schedule for Affective Disorders and Schizophrenia-Depression Rating Scale. Receiver Operating Characteristic curve analyses were conducted, with area under the curve (AUC) and Youden Index (J) as primary indices. We hypothesized that the lower limit of the 95% confidence interval for the area under the curve would be ≥ 0.70. Results: The primary analysis yielded an AUC of 0.85 (95% CI: 0.763 - 0.947) and an optimal cut-off of ≥43 (J = 0.60, positive predictive value = 91.4%, negative predictive value = 62.5%, sensitivity = 72.7%, specificity = 87.0%). Limitations: Our study collected a small sample, disproportionately consisting of adolescents that are White, female sex assigned at birth, identifying as girl/woman gender, born in Canada, and having other comorbid disorders. Conclusions: Our preliminary findings highlight the potential for the MFQ to support clinical decision-making relevant to adolescents experiencing varying severities of depressive symptoms in secondary care settings.