This work sought to determine functional social support in family caregivers of severely dependent elderly adults and its relationship with sociodemographic characteristics. This was a cross-sectional study. The Duke-UNC-11 Functional Social Support questionnaire was applied to 67 family caregivers from Family Healthcare Centers in Valdivia (Chile) in 2012. Family caregivers perceived low levels of affective social support (49.3%) and of trust (98.5%); considering insufficient the information and advice they receive related, principally, to the scarce number of people who help, they need to establish communication to share their feelings and problems derived from the task of caring. These caregivers recognize the support from community healthcare centers. Functional social support is correlated to the following variables: number of people who live in the home, years of study, age of the caregiver, and number of people who help; with this last variable predicting the level of social support in its two dimensions. Family caregivers of severely dependent elderly adults perceive a level of functional social support, especially in the dimension of trust. Community nurses must increase the number of home visits, evaluate the needs for social support perceived in caregivers, and teach coping strategies to mitigate problems that emerge in this work.