Organ-specific aging measures have recently gained growing attention. Still, the interpretation of the contributing factors, biological mechanism and relevance of the physiological insights remain unclear. Here, we quantified 639 circulating blood proteins in 6,211 Swedish twins from a population-based cohort (mean age 65±8 years; 57.8% female) to develop organ-specific aging clocks and provide an explorable web application. At sampling, organ aging aligned with lifestyle, clinical and prior disease profiles. Over a 15-year follow-up, organ aging was associated with age-related disease, multimorbidity, healthspan, and mortality, capturing both organ-specific and systemic effects. Greater burden of aged organs even marked poorer health trajectories. The twin-based analyses revealed moderate heritability and persistence of key health associations. Associations with mortality remained robust (cardiovascular age HR 2.20[1.69–2.85]; FDR