Some studies have demonstrated the relationship between social support networks (SSNs) and health status. In this sense, it has been considered that physical and mental functioning is a key indicator of the health in the age people. The aim of this study was to determine the association between social support networks and physical functioning. A cross-sectional study was carried out including a convenience sample of 150 older community-dwelling Mexicans. We assessed the familial, extra-familial and institutional SSNs; social contacts; the activities of daily living (ADL); the instrumental activities of daily living (IADLs); and physical functioning task (PFT) performance among study participants. Of the 150 older subjects, 53 reported living alone (35%), 113 (75%) reported having few SSNs, and 37 (25%) reported having enough SSNs. Persons with few familial SSNs were at increased odds of demonstrating dependence in at least one of the ADL (OR = 3.25, 95% CI 1.06–9.92, p < 0.05). Likewise, persons with few institutional SSNs and few social contacts were at increased odds of demonstrating dependence in at least one of the IADL (OR = 6.96, 95% CI 1.57–30.7, p < 0.01; OR = 5.02, 95% CI 1.44–17.5, p < 0.01, respectively). We also observed that having few extra-familial SSNs and few social contacts were the main risk factors for PFT dependence, with ORs of 3.70 (95% CI 1.21–11.2, p < 0.05) and 3.85 (95% CI 1.10–13.5, p < 0.05), respectively. Our findings suggest that having few SSNs could be a significant risk factor for reduced physical functioning in older adults.