The Consensus Sleep Diary (CSD) is a standardized, prospective tool for tracking nightly subjective sleep. The current study evaluated the validity and utility of the CSD, with consideration for challenges inherent to psychometric evaluation of diary measures. Results showed that the CSD indices differentiated good sleepers from those with insomnia and were associated with similar objective indices and a subjective insomnia severity measure. The ability to detect treatment improvements after cognitive behavior therapy for insomnia (CBT-I) was tested by comparing pre- and post-CBT-I CSD indices with a subjective rating of insomnia symptom severity. Improvement in insomnia symptom severity was significantly related to improvement on the CSD indices. Completion rate of the CSD amongst participants across all 14 days was 99.8%. These findings provide support for the validity, clinical utility, and usability of the CSD.