Japan has adopted community-based integrated long-term care, which has shifted the burden of care from institutions to the home. However, family caregivers have received less attention compared with care recipients. Many family caregivers are also older adults, and it is important that caregivers receive appropriate support to alleviate the burden of care. In rural and sub-urban area with limited resources compared to urban area, it is necessary to know which support to be prioritized. Therefore, this study aimed to understand family caregivers' perceptions of social support, the type and source of support which were considered important, and how it affected their caregiving burden and quality of life (QOL). We conducted a convergent mixed-method study with 174 primary family caregivers of older adults receiving home care in rural and suburb area of Central Japan. The mixed-method approach enabled qualitative data to complement quantitative results. Strong family support and higher education had positive effects on QOL, while higher caregiving burden and longer duration of care had negative effects on QOL. Provision of tangible support from family and healthcare professionals was central in reducing caregiving burden and improving caregivers' QOL. Support from distant relatives or neighbors, which was deemed inappropriate by caregivers, had a negative effect on caregivers' emotional status. In conclusion, family caregivers perceived support positively, but the effects depended on who provided support. While tangible support from close family and professionals was perceived positively, support from neighbors or distant relatives should consider caregivers' needs and condition to avoid a negative impact.