Background <p>There is no gold standard for assessment of medication adherence. This study aimed to systematically review the literature to identify validated medication adherence measurement tools and methods used in clinical practice and research settings in the context of patients with chronic kidney disease (CKD) and to synthesize key features of the identified medication adherence tools.</p> Methods <p>We systematically reviewed MEDLINE via Ovid, Embase via Ovid, Cochrane Central Register of Controlled Trials (CENTRAL), and CINAHL (via EBSCO) from inception to September 25, 2025. All abstracts were screened by pairs of reviewers independently, followed by a full-text review identifying the tool/method used for measuring medication adherence. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to conduct this systematic review. General study and medication adherence method/tool-specific characteristics were summarized. The quality criteria for measurement properties were applied across the included studies to synthesize and assess the strength of the evidence.</p> Results <p>The 43 included articles originated from 25 countries. The most common measures used for evaluating medication adherence were the Eight-Item Morisky Medication Adherence Scale (MMAS-8) (<i>n</i> = 11 [25.6%]), Medication Possession Ratio (MPR) (<i>n</i> = 10 [23.3%]), Proportion of Days Covered (PDC) (<i>n</i> = 8 [18.6%]), and Medication Events Monitoring System (MEMS) (<i>n</i> = 6 [14.0%]). Five (15.6%) studies used multiple methods to measure medication adherence.</p> Conclusion <p>No accepted reference tool is available to measure CKD patients’ medication adherence. Some tools, however, were used more frequently in the context of patients with CKD. Choosing an appropriate method/tool or a combination of methods depends on the clinician/researcher’s goals, study setting, availability of data and other resources, and patients’ characteristics.</p>