<p>Electrochemistry, a fundamental subject in chemistry education, is frequently regarded as challenging by chemistry teachers. This study developed an assessment instrument to measure chemistry teachers’ understanding of electrochemistry. By examining essential questions, we delineated four fundamental sub-domains of electrochemistry and constructed a three-level hypothetical model using the historical, educational, and systems thinking perspectives. The instrument underwent a pilot test with 54 chemistry teachers and received feedback for the instrument revision. Subsequently, a field test encompassed a broader demographic of 138 chemistry teachers. This study employed the Rasch modeling approach to analyze the data that provides evidence for the instrument’s reliability and validity. The final vision of the Teachers’ Understanding of Electrochemistry Measurement (TUEM) comprises four two-tier multiple-choice questions and eleven open-ended questions, with empirical results that align well with the hypothetical understanding levels. The findings have practical implications for chemistry teachers’ assessment, professional development, and electrochemistry education.</p>