Background: Adherence to drug prescriptions is often suboptimal among heart failure (HF) patients. Informed decision-making may improve patients' adherence to HF drug prescriptions. Aims of the study: We aimed to test whether a self-study-based informed decision-making tool could improve adherence to drug prescriptions among ambulatory HF patients. Methods: A tool and a statement-based questionnaire were developed to evaluate drug adherence willingness based on COMPAR-EU recommendations. The test group (n = 40) was exposed to the tool + questionnaire; controls (n = 40) answered the questionnaire only. Agreement with statements of the questionnaire was graded on a scale of 0 to 4 points, reflecting no to full agreement. Results: The median age of controls was younger (56 vs. 61 years; p = 0.04); test and control group patients did not differ across other parameters (always p > 0.05). Patients in both groups agreed that "HF is a life-long disease" (3.5 vs. 4; p = 0.19) and that "only life-long drug treatment provides benefit" (4 vs. 4; p = 0.22). More test group patients confirmed improved comprehension of HF disease (3 vs. 2; p = 0.03) and greater acceptance that "achievement of benefit asks for a combination of HF drugs" (4 vs. 3; p = 0.009) and "daily intake" (4 vs. 3; p = 0.004). In test group patients, questions remained, resulting in less agreement that "all aspects of my heart disease" are understood (1 vs. 3; p < 0.001). Willingness to adhere to HF-drug treatment was not different between the groups (3 vs. 3.5; p = 0.28). Conclusions: The self-study-based informed decision-making tool improved the comprehension of HF and the need for HF treatment, but did not improve willingness to adhere since questions remained unanswered.