This study determined the sensitivity and specificity of the telephone-administered Minnesota Cognitive Acuity Screen (MCAS) to distinguish mild cognitive impairment (MCI) from healthy controls (HCs) and from Alzheimer’s disease (AD). A total of 100 individuals with MCI, 50 individuals with possible/probable AD, and 50 HCs were screened to exclude medical and psychiatric conditions affecting cognition. In-office evaluation included neuropsychological testing, neurologic examination, and neurodiagnostic work-up. Participants with AD obtained significantly lower MCAS total scores than participants with MCI, who in turn performed worse than the HC group. Sensitivity was 86% and specificity was 78% for distinguishing between MCI and HC. Sensitivity was 86% and specificity was 77% for discriminating between MCI and AD. Sensitivity was 91% and specificity was 78% for discriminating between impaired groups (MCI and AD) and HCs. Results suggest that the MCAS successfully discriminates MCI from HC and AD and has potential as an effective telephone-administered screening tool for memory disorders.