Objective To investigate the psychiatric and behavioral symptoms of dementia comorbidity patients, and their caregivers' management strategies and levels of grief, and to construct a mediation model to analyze the relationships among the three variables. Methods A total of 212 caregivers of dementia comorbidity patients were investigated by using a general information questionnaire for patients and caregivers, the Marwit Meuse Caregiver Grief Inventory-Short Form (MM-CGI-SF), the Neuropsychiatric Inventory-Questionnaire (NPI-Q), and the Dementia Management Strategies Scale (DMSS). Results The participants′ total score of NPI-Q was 6.0 (4.0, 7.0), MM-CGI-SF was 59.5 (45.0, 82.0), and their subscale scores of criticism, encouragement, and active management in DMSS were 26.0 (18.0, 40.0), 34.0 (26.0, 42.0), and 46.5 (40.3, 50.0), respectively. Active management played as a mediator between the severity of psychiatric and behavioral symptoms in patients and caregiver grief, with the mediating effect accounting for 23.4% of the total effect. Conclusion The severity of psychiatric and behavioral symptoms in dementia comorbidity patients not only directly predicts caregiver grief, but also indirectly influences caregiver grief through caregivers′ active management strategies. It is recommended to establish a family-centered care model, encourage the involvement of all family members to help caregivers adopt active management strategies in coping with patients′ disease symptoms.