Documentation of language usage in medical settings could be effective in identifying and addressing language barriers and would improve understanding of health disparities. This study evaluated the availability and accuracy of medical records information on language for 1,664 cancer patients likely to have poor English proficiency. Accuracy was assessed by comparison to language obtained from interview-based research studies. For patients diagnosed at facilities where information on language was not abstracted electronically, 81.6% had language information in their medical records, most often in admissions documents. For all 37 hospitals, agreement between medical records and interview language was 79.3% overall and was greater for those speaking English than another language. Language information is widely available in hospital medical records of cancer patients. However, for the data to be useful for research and reducing language barriers in medical care, the information must be collected in a consistent and accurate manner.