Background: Volunteers have been a valuable resource in supporting people with dementia and their caregivers in the community. However, factors such as misconceptions, negative attitudes towards dementia, and a lack of motivation might impact the quality of volunteer care. The aim of the present paper is to examine the effect of training and service provision on the knowledge and attitudes of volunteers towards dementia, as well as the association between such knowledge and attitudes and the motivation to volunteer. Methods: The present study is part of an effectiveness-implementation cluster randomized clinical hybrid trial using a music-with-movement intervention to promote the well-being of people with dementia and their informal caregivers. Volunteers were recruited to receive training to support the delivery of the intervention. Training and enrichment workshops were offered to volunteers during the one-year project. Before and after their volunteer training and service, the recruited volunteers were asked to complete the following assessments: The Volunteer Functions Inventory, Dementia Attitudes Scale, and the Alzheimer’s Disease Knowledge Scale. Wilcoxon signed-rank test and multiple regression test were applied for statistical analyses. Results: A total of 127 volunteers were recruited and 81 of them completed a mean period of 47.32 weeks of training and service. Significant improvements in their total score on the Alzheimer’s Disease Knowledge Scale (p=.009) and Dementia Attitudes Scale (p<.001) were found. Dementia knowledge (β=.57, p<.001) and attitudes (β=-.18, p=.038) were found to have the most significant association with the motivation to be a volunteer at baseline. Conclusions: The present study illustrated the importance of quality volunteer training and voluntary service in improving the dementia knowledge and attitudes of volunteers. It also shed light on the association between knowledge and attitudes with the motivation to volunteer. Accordingly, future research and public health policymakers should address more efforts to amplify the advantage of volunteers as a vital asset in dementia care.Trial Registration: NCT03575026 (ClinicalTrials.gov), First registeration on 02/07/2018.