In many healthcare systems, the outcomes of care for patients with heart failure (HF) are in need of improvement. By applying telemonitoring, this study aimed to assess its short-term impact on patients' disease-specific knowledge, adherence, and depression. As part of a larger trial (N = 1,023, 17 centers), this study reports preliminary findings among 101 patients from three Dutch hospitals. Patients were randomized to receive care using telemonitoring or standard care. Data concerning patients' disease-specific knowledge, adherence to pharmacological and nonpharmacological recommendations, and depression were collected by postal questionnaires. In this study, data collected before randomization and 3 months afterwards were analyzed. Disease-specific knowledge improved significantly in two of the three hospitals (p < 0.001 and p = 0.040). Adherence in terms of fluid restrictions (p = 0.012), daily weighing (p < 0.001), physical exercising (p = 0.034), and alcohol restrictions (p = 0.040) improved significantly in the telemonitoring group. Additionally, in contrast with the hypothesized increase of depression, the use of telemonitoring resulted in a substantial but statistically not significant decrease in depression. The improved adherence rates within the 3-month study period underscore the potential of telemonitoring to enhance self-management among HF patients and consequently its potential impact on other outcomes. Longer-term results will enable solid conclusions to be reached concerning the relation between telemonitoring and patients' adherence.