Objective To compare the effectiveness of two “treatments”—early, intensive home health nursing and physician follow‐up within a week—versus less intense and later postacute care in reducing readmissions among heart failure (HF) patients discharged to home health care. Data Sources National Medicare administrative, claims, and patient assessment data. Study Design Patients with a full week of potential exposure to the treatments were followed for 30 days to determine exposure status, 30‐day all‐cause hospital readmission, other health care use, and mortality. An extension of instrumental variables methods for nonlinear statistical models corrects for nonrandom selection of patients into treatment categories. Our instruments are the index hospital's rate of early aftercare for non‐HF patients and hospital discharge day of the week. Data Extraction Methods All hospitalizations for a HF principal diagnosis with discharge to home health care between July 2009 and June 2010 were identified from source files. Principal Findings Neither treatment by itself has a statistically significant effect on hospital readmission. In combination, however, they reduce the probability of readmission by roughly 8 percentage points (p < .001; confidence interval = −12.3, −4.1). Results are robust to changes in implementation of the nonlinear IV estimator, sample, outcome measure, and length of follow‐up. Conclusions Our results call for closer coordination between home health and medical providers in the clinical management of HF patients immediately after hospital discharge.