Under-diagnosis and under-treatment of depression are major problems in nursing home residents. The purpose of this study was to determine antidepressant use among nursing home residents who were diagnosed with depression using three different methods: (1) the Geriatric Depression Scale, (2) Minimum Data Set, and (3) primary care provider assessments. As one would expect, the odds of being treated with an antidepressant were about eight times higher for those diagnosed as depressed by the primary care provider compared to the Geriatric Depression Scale or the Minimum Data Set. Men were less likely to be diagnosed and treated with antidepressants by their primary care provider than women. Depression detected by nurses through the Minimum Data Set was treated at a lower rate with antidepressants, which generates issues related to interprofessional communication, nursing staff communication, and the need for geropsychiatric role models in nursing homes.