This study examined the reciprocal relationships between perceived mastery, stress, and three functional areas of social support: tangible support, informational support, and belongingness support. Data were collected during two face-to-face interviews with a sample of low-income, primarily African American mothers, conducted approximately one year apart. Consistent with predictions, initial levels of mastery predicted higher subsequent levels of instrumental social supports (tangible and advice support), but were unrelated to belonging support. Conversely, initial levels of tangible support were predictive of later mastery. Perceived stress did not account for any additional variance in subsequent support, although initial levels of belonging support only did predict reduced stress at Time 2. Results suggest that successful attempts to garner instrumental supports is an important contributor to individuals’ sense of self-efficacy, while at the same time, self-efficacy leads to more successful use of existing social support systems. These findings point to the importance of having both available tangible support networks as well as close emotional supports for low-income parents. The importance of using longitudinal, multi-dimensional analyses to better understand the social support process is discussed.