The Mini-Mental State Examination (MMSE) is one of the most commonly used instruments to screen for cognitive deficits within the hospital setting. However training in how to administer this widely used tool is scarce with little, if any, formal training for nursing staff. Scores are also often misused with over reliance on results and cut-offs to support a diagnosis of dementia within the acute and sub-acute aged care context. The present study assessed the level of training and accuracy in administering the MMSE within a geriatric in-patient rehabilitation ward. Ratings of the level of knowledge, training and confidence in administering the MMSE were obtained from 16 registered nurses and two medical officers before and after an education session on the uses of the MMSE and correct administration. Objective assessment of competencies in administration was also obtained with interrater reliability scores demonstrating high accuracy in the use of this screening instrument. Knowledge improved following the training session, but confidence scores remained unchanged. Results also indicated limited knowledge regarding the necessity for cognitive screening in an aged care setting. Inconsistency in administration of certain items was also identified as a concern. Strategies for improving the quality of administration are identified and discussed.