Policymakers and educators have increasingly focused on improving public understanding of climate change to prepare people to tackle its causes and impacts. Researchers have joined these efforts by assessing environmental literacy (EL) and climate change literacy (CCL) to inform policies and educational initiatives. This article systematically reviews CCL assessment trends and methods by analyzing papers from Scopus and ScienceDirect. The findings reveal a variety of approaches to defining and measuring CCL. Variations were also observed in the styles of presenting CCL levels. Based on the review, we propose standardizing CCL assessment by defining core and optional domains, aiming to cater to the diverse needs of groups seeking to measure CCL for different purposes. We also suggest that policymakers and educators can glean more nuanced insights from results when CCL levels are measured using three or more proficiency levels. Lastly, we recommend that future studies investigate the CCL-climate action relationship to ensure that CCE programs are designed based on evidence of CCL-climate action connections.