Recombinant human erythropoietin (rhEPO) is one of the most important biopharmaceuticals worldwide, with global sales expected to reach US$11.9 billion in 2020. The charge heterogeneity of rhEPO must be monitored throughout the entire production process. Imaged capillary isoelectric focusing (icIEF) is a promising method for monitoring rhEPO charge heterogeneity, but it must be validated according to the ICH guideline (International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use). Here, a multi-laboratory joint method validation of the icIEF method for rhEPO analysis was performed according to the ICH Harmonized Tripartite Guideline on Analysis Procedure. This guideline includes specificity, precision, accuracy, linearity, range, LOQ and robustness, whereby precision is defined by the repeatability, intermediate precision and reproducibility.