Objectives This study investigated the short-term impact and the retention of a dementia care intervention for healthcare staff working in an Italian acute hospital setting. Additionally, we identified the predictors of improvement across the intervention. Method Sixty-two healthcare staff from an Italian public hospital participated in a dementia care intervention consisting of 5 modules delivered in a 5-hour training program focusing on dementia management, knowledge, and care. A pre-test/post-test and six-months follow-up design was used to evaluate participants’ changes in knowledge, attitudes, and confidence in dementia. Results The intervention significantly improved healthcare staff’s dementia knowledge and confidence immediately after the end of the intervention. No significant changes were observed from post-test to follow-up, indicating retention of these outcomes over six months. Regarding attitude to dementia, we found an immediate improvement only in the Recognition of Personhood scale. Looking at the predictors of improvement, healthcare staff with lower levels of knowledge, attitudes, and confidence in dementia at pre-test were those who improved more following the intervention. Conclusion These findings provide further evidence that dementia care interventions are suitable initiatives to promote knowledge and skills required to manage the needs of people with dementia in an acute hospital setting.