Identifying aging-associated biomarkers applicable for multiple tissues is challenging but crucial for assessing tissue aging. Here, we obtained and analyzed 456 transcriptomes on 17 organs from 30 C57BL/6 J mice with different ages, revealing the consistently upregulated mRNAs of Ighm, C4b, and Ccl8 in most aged organs. This finding received support from independent transcriptomic and proteomic datasets and was further validated through western blot, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence, arguing for both Ighm mRNA and protein as tissue-level aging biomarkers, at least in mice. Its sensitivity to antiaging interventions further emphasizes the significance of Ighm in assessing tissue aging in mice.