The increasingly transdisciplinary context of design, where designers collaborate with other disciplinary and domain experts, means there is a growing need to evidence the effectiveness of design methods. We address this need in two ways. First, we propose a ‘chain of evidence’, from motivation to claims, operationalising this in a systematic assessment framework. Second, we systematically review current design method research. Our results reveal that while all links in the chain of evidence are reported across the literature and best practices can be identified, no individual paper either reports all links or consistently achieves best practice. Our framework and results demonstrate the need for standards of evidence in this area, with implications for design method research, development, education, and practice.