Objective:to analyze the relationship between postural instability and the condition and markers of physical frailty of the elderly people in outpatient geriatric and gerontology care.Method:a cross-sectional study with a sample of 381 elderly subjects. Physical frailty was evaluated by the frailty phenotype and postural instability through the Berg Balance Scale. Univariate analyses consisted in Chi-square tests, and multivariate analyses used the Forward Stepwise method, which resulted in a model of physical frailty associated with postural instability.Results:among the participants, 56 (14.7%) were frail, 217 (57%) pre-frail, and 68 (28.3%) non-frail. Pre-frailty (p < 0.001), frailty (p = 0.000), and the markers hand grip strength (p = 0.0008), unintentional weight loss (p = 0.0094), level of physical activity (p = 0.0001), fatigue/exhaustion (p = 0.0001), and gait speed (p = 0.0001) were associated with postural instability.Conclusion:the presence of postural instability determines a greater chance of the elderly being frail or pre-frail. This result favors the planning of gerontological nursing care and strengthens the treatment plan under a specific approach.