Cities increasingly invoke the Sustainable Development Goals (SDGs) as an organising language for climate action, liveability, innovation, and inclusive development. Yet the use of SDG vocabulary does not by itself demonstrate institutional change. This article examines how Agenda 2030 has been incorporated into the strategic governance of Espoo, Finland’s second-largest city, and asks how far SDG localisation has progressed from strategic commitment to routine administrative practice. The study is grounded in a directed qualitative secondary analysis of a published interview corpus consisting of twelve expert interviews conducted in April–June 2021 with councillors, city managers, sectoral administrators, university representatives, a technology-sector stakeholder, and national and European governance actors. Building on the empirical record of that case, the article develops a five-stage SDG governance maturity framework and evaluates six dimensions of institutional embedding: strategic anchoring, horizontal coordination, ecosystem co-production, policy instrumentation, accountability and temporal continuity, and monitoring and learning. The findings show that Espoo displays a comparatively advanced form of SDG localisation. Agenda 2030 is embedded in the Espoo Story, cross-sectoral development programmes, and collaboration with Aalto University and business partners. At the same time, the evidence also shows that sustainability is not yet consistently built into ex ante policy preparation; the SDGs are often considered only after policy choices have been shaped, accountability remains diffuse, and four-year council cycles complicate long-horizon implementation. The article argues that the decisive threshold in urban SDG governance is the movement from narrative alignment to procedural embedding. By translating qualitative evidence into a governance maturity framework, the study offers a practical analytical tool for urban development and smart-city research, especially for cities seeking to connect strategic ambition, service innovation, and institutional reform.