cPRISM-SRM is an extension of MS-based proteomic analysis with the key feature of being able to characterize low numbers of mammalian cells. Compared to current targeted MS methods, CPRISM-SRM requires 3–4 orders of magnitude lower cell numbers. The method capitalizes on using ""carrier protein"" to assist processing of low numbers of cells with minimal loss, high-resolution PRISM separation for target peptide enrichment, and sensitive-targeted MS (SRM) for protein quantification. cPRISM-SRM has sufficient sensitivity to quantify proteins expressed at ≥200,000 copies per cell at the single-cell level and ≥3000 copies per cell in 100 mammalian cells. With further improvement cPRISM-SRM has the potential to move toward targeted MS-based single-cell proteomics.