Introduction: This study used extended theory of planned behavior (extended TPB) to understand the underlying factors related to help-seeking behavior for sexual problems among Iranian women with heart failure (HF). Methods: We recruited 758 women (mean age = 61.21 ± 8.92) with HF at three university-affiliated heart centers in Iran. Attitude, subjective norms, perceived behavioral control, behavioral intention, self-stigma of seeking help, perceived barriers, frequency of planning, help-seeking behavior, and sexual function were assessed at baseline. Sexual function was assessed again after 18 months. Structural equation modeling was used to explain change in sexual functioning after 18 months. Results: Attitude and perceived behavioral control were positively correlated to behavioral intention. Behavioral intention was negatively and self-stigma in seeking help was positively correlated to perceived barriers. Behavioral intention was positively and self-stigma in seeking help was negatively correlated to frequency of planning. Perceived behavioral control, behavior intention, and frequency of planning were positively and self-stigma in seeking help and perceived barriers were negatively correlated to help-seeking behavior. Help-seeking behavior was positive correlated to the change of FSFI latent score. Conclusions: The extended TPB could be used by healthcare professionals to design an appropriate program to treat sexual dysfunction in women with HF.