Background: Medical research increasingly utilizes patient-reported outcome measures administered and scored in different languages. In order to pool or compare outcomes from different language versions, instruments should be measurement equivalent across linguistic groups. The objective of this study was to examine the cross-language measurement equivalence of the Patient Health Questionnaire-9 (PHQ-9) between English- and French-speaking Canadian patients with systemic sclerosis (SSc). Methods: The sample consisted of 739 English- and 221 French-speaking SSc patients. Multiple-Indicator Multiple-Cause (MIMIC) modeling was used to identify items displaying possible differential item functioning (DIF). Results: A one-factor model for the PHQ-9 fit the data well in both English- and French-speaking samples. Statistically significant DIF was found for 3 of 9 items on the PHQ-9. However, the overall estimate in depression latent scores between English- and French-speaking respondents was)