Family or friend caregivers’ concerns about assisted living (AL) residents’ mental health are reflective of poor resident and caregiver mental health. COVID-19-related visiting restrictions increased caregiver concerns, but research on these issues in AL is limited. Using web-based surveys with 673 caregivers of AL residents in Western Canada, we assessed the prevalence and correlates of moderate to severe caregiver concerns about residents’ depressed mood, loneliness, and anxiety in the 3 months before and after the start of the COVID-19 pandemic. Caregiver concerns doubled after the start of the pandemic (resident depressed mood: 23%–50%, loneliness: 29%–62%, anxiety: 24%–47%). Generalized linear mixed models identified various modifiable risk factors for caregiver concerns (e.g., caregivers’ perception that residents lacked access to counseling services or not feeling well informed about and involved in resident care). These modifiable factors can be targeted in efforts to prevent or mitigate caregiver concerns and resident mental health issues.