OBJECTIVES To explore the association of psychological and social well-being with unplanned hospital utilization in an older Swedish population. DESIGN Data for this study were gathered from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K). Information on hospital care use was extracted from the Stockholm County Council Inpatient Register for up to 4 years after the baseline SNAC-K assessment (2001-2007). Participants with dementia or living in institutions were excluded from the study sample. SETTING Community-based study of randomly selected adults, aged 60 years or older, living in the Kungsholmen district of Stockholm. PARTICIPANTS A complete case analysis was performed on 2139 individuals. MEASUREMENTS We created standardized indexes of psychological well-being (integrating life satisfaction and positive and negative affect) and social well-being (integrating social connections, support, and participation). Negative binomial models were used to estimate the association of psychosocial well-being with unplanned admissions, hospital days, and 30-day readmissions, considering potential sociodemographic, lifestyle, personality, and clinical confounders. RESULTS Individuals with psychological well-being scores above the median had lower rates of unplanned hospital admissions (incidence rate ratio [IRR] = 0.67; 95% confidence interval [CI] = 0.55-0.82) and hospital days (IRR = 0.67; 95% CI = 0.49-0.92) compared to those with scores below the median. High levels of social well-being were also protective for unplanned admissions and hospital days, but the statistical significance was lost in the fully adjusted models. Relative to individuals with low well-being on both indexes, the rate of unplanned admissions and hospital days was lowest in those with both high psychological and social well-being (IRR = 0.72; 95% CI = 0.55-0.93; and IRR = 0.57; 95% CI = 0.39-0.85, respectively). For 30-day readmissions, a statistically significant negative association was found with psychological well-being, but only when operationalized as a continuous variable. CONCLUSION Given their association with unplanned admissions and hospital days, targeting aspects of psychosocial well-being could be a viable strategy for reducing healthcare use and, eventually, costs.