Abstract Background Medication nonadherence contributes to hospitalizations in recently discharged patients with heart failure (HF). We aimed to test the feasibility of telemonitoring medication adherence in patients with HF. Methods and Results We randomized 40 patients (1:1) hospitalized for HF to 30 days of loop diuretic adherence monitoring with telephonic support for nonadherence or to passive adherence monitoring alone. Eighty-three percent of eligible patients agreed to participate. The median age of patients was 64 years, 25% were female, and 45% were Hispanic. Overall, 67% of patients were nonadherent (percent of days correct number of doses taken <88%). There were no differences between intervention and passive monitoring group patients, respectively, in adherence (median correct dosing adherence 82% versus 73%; p = 0.41) or in the proportion readmitted within 30 days (30% versus 20%; p = 0.72). Eighty-eight percent of patients rated the wireless electronic adherence device as somewhat or very easy to use, and 88% agreed to use it again. Conclusions Adherence telemonitoring was acceptable to most patients with HF. Diuretic nonadherence was common even when patients knew they were being monitored. Future studies should assess whether adherence telemonitoring can improve adherence and reduce readmissions among patients with HF.