Background: The 9-item European Heart Failure Self-Care Behavior scale (EHFScB-9) is a self-reported questionnaire commonly used to capture the self-care behavior of people with heart failure (HF). Objective: The aim of this study was to investigate the EHFScB-9's factorial structure and categorical functioning of the response scale and differential item functioning (DIF) across subpopulations in Iran. Methods: Patients with HF (n = 380; 60.5% male; mean [SD] age, 61.7 [9.1] years) participated in this study. The median (interquartile range) of the duration of their HF was 6.0 (2.4-8.8) months. Most of the participants were in New York Heart Association classification II (NYHA II, 61.8%); few of them had left ventricular ejection fraction assessment (11.3%). All participants completed the EHFScB-9. Confirmatory factor analysis was used to test the factorial structure of the EHFScB-9; Rasch analysis was used to analyze categorical functioning and DIF items across 2 characteristics (gender and NYHA). Results: The 2-factor structure ("adherence to regimen" and "consulting behavior") of the EHFSCB-9 was confirmed, and the unidimensionality of each factor was found. Categorical functioning was supported for all items. No items displayed substantial DIF across gender (DIF contrast, -0.25-0.31). Except for item 3 ("Contact doctor or nurse if legstfeet are swollen"; DIF contrast, -0.69), no items displayed substantial DIF across NYHA classes (DIF contrast, -0.40 to 0.47). Conclusions: Despite the DIF displayed in 1 item across the NYHA classes, the EHFScB-9 demonstrated sound psychometric properties in patients with HF.