Objective To evaluate whether communication failures between home health care nurses and physicians during an episode of home care after hospital discharge are associated with hospital readmission, stratified by patients at high and low risk of readmission. Data Source/Study Setting We linked Visiting Nurse Services of New York electronic medical records for patients with congestive heart failure in 2008 and 2009 to hospitalization claims data for Medicare fee‐for‐service beneficiaries. Study Design Linear regression models and a propensity score matching approach were used to assess the relationship between communication failure and 30‐day readmission, separately for patients with high‐risk and low‐risk readmission probabilities. Data Collection/Extraction Methods Natural language processing was applied to free‐text data in electronic medical records to identify failures in communication between home health nurses and physicians. Principal Findings Communication failure was associated with a statistically significant 9.7 percentage point increase in the probability of a patient readmission (32.6 percent of the mean) among high‐risk patients. Conclusions Poor communication between home health nurses and physicians is associated with an increased risk of hospital readmission among high‐risk patients. Efforts to reduce readmissions among this population should consider focusing attention on this factor.