Purpose of the Study: This study examines the association between nursing home accreditation and deficiency citations. Design and Methods: Data originated from a web-based search of The Joint Commission (TJC) accreditation and On-line Survey Certification of Automated Records from 2002 to 2010. Deficiency citations were divided into 4 categories: resident behavior and facility practices, quality of life, quality of care, and the most severe citations. Data were analyzed through negative binomial regression, where the number of residents at risk for each measure was the exposure level for that measure. Results: TJC-accredited nursing homes had fewer deficiency citations in all 4 deficiency categories examined. Comparing citations in the year of accreditation with the first year after accreditation, 3 of the 4 deficiency categories were significant. In comparing deficiency citations after 8 years of accreditation, all 4 categories of deficiencies were significant. In all cases, accreditation was associated with fewer deficiency citations. Implications: Our results indicate that TJC-accredited nursing homes improve their quality immediately after accreditation and continue to maintain these improvements over the long-term. These findings support the need for further discussion and facilitation of voluntary accreditation in nursing homes.