Lean body mass loss has been indicated as a reliable marker of frailty and poor physical performance among older individuals. We evaluated the relationship between calf circumference and frailty, physical performance, muscle strength, and functional status in persons aged 80 years or older. Data are from the baseline evaluation of the Aging and Longevity Study in the Sirente geographic area (ilSIRENTE Study) (n = 357). The calf circumference was measured at the point of greatest circumference. Frailty was categorized according to the present of slow gait speed, weakness, weight loss, energy expenditure and exhaustion. Physical performance was assessed using the physical performance battery score, which is based on three timed tests: 4-m walking speed test, the balance test and the chair stand test. Analyses of covariance were performed to evaluate the relationship between different calf circumference and physical function. After adjustment for potential confounders, which included age, gender, education, body mass index, sensory impairments, cerebrovascular diseases, albumin, reactive C protein, interleukine-6, and cholesterol, physical performance (SPPB score: 7.27 versus 6.18, p = 0.02) and muscle strength (Hand Grip: 32 kg versus 28 kg, p = 0.03) measures significantly improved as calf circumference increased. The frailty index score was significantly lower among subjects with higher calf circumference (1.66 versus 2.17, p = 0.01). The present study suggests that among community-dwelling older people, calf circumference may be positively related to lower frailty index and higher functional performance. As such, calf circumference is a valuable tool for guiding public health policy and clinical decisions.