For more than 60 years, residents of the villages on the Techa River have been chronically exposed to combined radiation, receiving a wide range of doses. Red bone marrow (RBM) is the critical system in the exposure conditions. This study aimed to assess the effect of chronic exposure on premature aging of T-lymphocytes based on the frequency of unstable chromosome aberrations; the subjects were the residents of the Southern Urals that have been chronically exposed to radiation. The increased frequency of occurrence of dicentrics and rings in T-cells of the exposed persons was the marker of cellular aging, with the associated doses to the red bone marrow (RBM dose) at 0.5–2.5 Gy. The participants (RBM donors), both exposed and non-exposed, were divided into three age subgroups: 40–59 years old, 60–69 years old, 70–79 years old. The differences in the RBM dose among the exposed individuals were insignificant. In the exposed group, unstable chromosome aberrations (UCA) were recorded significantly more often than in the control group (p = 0.04). The age group of 40–59 years was the one where the exposed donors had significantly more frequently occurring chromosome aberrations compared to the non-exposed participants. There were no such differences registered in other age groups. The age-associated increase of the amount of chromosome aberrations was registered in the non-exposed group only. Chronic exposure to radiation indirectly promotes premature aging of T-lymphocytes: 1) in the long term, the exposed individuals had UCA significantly more often; 2) compared to the control group, the 40–59 years age subgroup of the exposed group had increased cytogenetic index. In the context of this study, the number of dicentrics and rings was not registered as increasing in the older age subgroups of exposed individuals, which may be due to the specifics of the donor inclusion criteria, which, for the elderly, may favor radioresistant individuals.