Organisations preparing for the European Sustainability Reporting Standards (ESRS) mandate often lack a clear, structured approach to assess the maturity of their Environmental, Social, and Governance (ESG) capabilities. This study develops an ESG-specific Capability Maturity Model (ESG-CMM) through a six-step Design Science Research process. A systematic review distilled 104 descriptors from 15 capability maturity model articles. Open coding, cross-checked against ESRS topics, condensed these into 13 parameters arranged within five transversal clusters and five classic CMM levels. The artefact was demonstrated in a mid-sized manufacturing firm via seven semi-structured interviews. Evidence-backed ratings placed the organisation at Level 2.0 (“Repeatable”), highlighting strengths in governance policy and gaps in analytics capability and integrated risk management. The ESG-CMM artifact thus bridges a documented academic gap by translating a software-derived maturity logic to ESG practice, offering managers a self-assessment tool that is both regulator aligned and implementation oriented. While the single-case design limits generalisability, the research sets a foundation for multi-site validation and for sensor-driven, real-time scoring extensions.