Significance Long-lived proteins in extracellular spaces (joints/tissues) or within specialized nondividing cells (eye-lens) are associated with age-related decline. However, aging also occurs in dividing stem cells. Although several hypotheses have been proposed to explain how stem cells age, none have addressed whether long-lived proteins contribute to aging, partially because of technical challenges in identifying such proteins. We developed a method to overcome these limitations in the model system Saccharomyces cerevisiae . We identified two classes of long-lived asymmetrically retained proteins (LARPs). Full-length LARPs remain intact throughout the mother cell lifespan and accumulate in abundance or become posttranslationally modified. Fragmented LARPs are original proteins that are partially degraded, yet retained by the mother cell during aging. We speculate that LARPs contribute to the aging process.