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Reagent storage has been a long-standing challenge for diagnostics, especially those designed for low-resource settings and point-of-care applications. In general, the stability of a reagent relies on careful temperature control, often by refrigeration, which is costly and often unavailable in these remote settings. Poor reagent integrity can negatively affect the reproducibility and reliability of an assay. Given the recent interest in paper-based devices designed for quantitative analysis in point-of-care settings, a better understanding of reagent stability on filter paper is critical for proper device use and its longevity. In this article, we present an independent method to examine the stability of reconstituted antibodies that were stored on filter paper using flow cytometry. We validated the method by measuring the activity as measured by the mean fluorescence intensity (MFI) of antibodies stored with known stabilizers. Furthermore, we demonstrated the potential of our method to screen the influence of other paper treatments and storage processes on antibody stability, which may be applicable to the storage of reagents on paper in general.