We conducted an observational cross-sectional study to explore whether food insecurity or undernutrition was associated with frailty or low physical functioning in aging persons with HIV (PWH). Forty-eight PWH aged 50 years and older were enrolled. Independent samples t-tests and chi-square tests were used to examine the relationship of food insecurity or undernutrition to frailty or physical function. Participants were 58.6 (±6.3) years old, 83% male, 77% White, 21% Hispanic. In total, 44% experienced food insecurity and 71% experienced undernutrition, whereas 23% were frail and 69% were prefrail. Food insecurity was associated with impaired total short physical performance battery score (p = .02), impaired balance (p = .02), slower chair rise time (p = .03), and weight loss within 12 months (p = .05). Undernutrition was related to female gender (p = .01), worse frailty (p = .04), and weaker grip strength (p = .03). In this sample of undernourished and frail PWH, strong relationships between undernutrition and frailty were observed.