Interleukin-5 (IL-5) binding to interleukin-5 receptor subunit alpha (IL-5Rα) increases the number of eosinophils and enhances eosinophil activity. This leads to eosinophil tissue infiltration and damage to the lungs, ultimately resulting in exacerbation of asthma. Antibodies that block IL-5 binding to IL-5Rα are thought to play an important role in advanced asthma. Currently, key methods used to screen for targeted drugs are Surface Plasmon Resonance which is costly and anti-proliferation assays which are tedious and have a low signal-to-noise ratio. Here we describe a Fluorescence Activated Cell Sorting (FACS) assay, based on human embryonic kidney (HEK)- 293 cells with stable expression of IL-5Rα and the cytokine receptor common subunit beta (CSF2RB). Cells co-expressing IL-5Rα and CSF2RB had a 16% increase in the ability to bind IL-5 compared to cells expressing only IL-5Rα. The optimal concentration of IL-5 for the FACS assay was 0.1 μg/mL. The established FACS was used to screen anti IL-5 nanobodies and hybridoma supernatants for candidate antibodies that block the IL-5/IL-5α interaction. When compared to anti-proliferation assays, this method saved up to 90% of the assay time, offering the advantage of rapidity and accuracy in vitro. The assay described here provides a novel approach for rapid screening of IL-5/IL- 5Rα blocking antibodies in vitro to accelerate the development of drugs for asthma.