This study examines toponymic dissonance, the systematic semantic asymmetry and translational non-equivalence between Chinese (Cantonese) and Portuguese street names in Macau, as a case of post-colonial heritage governance operating under the “One Country, Two Systems” framework. Drawing on 1255 streets documented in Macau’s official street registries, the study is situated at the intersection of translation studies, critical toponymy, linguistic landscape research, post-colonial urban studies, and heritage governance. The analysis works from two classificatory instruments: (i) a four-dimensional coding system distinguishing anthroponymic, toponymic, functional/descriptive, and abstract/idealistic naming sources; (ii) a four-tier semantic distance evaluation (Levels 0–3) that quantifies the divergence between the official Portuguese name and the locally negotiated Cantonese name. Empirically, 439 of 1255 streets (35.0%) exhibit “complete asymmetry” (Level 3), wherein Chinese and Portuguese names derive from irreconcilably different semantic sources; this paper identifies five principal types of asymmetry, ranging from political commemoration versus functional or geographic description to the de-institutionalisation of colonial administrative references. Crucially, the study also engages the contemporary multilingualisation of Macau’s linguistic landscape, in which English, Tagalog, Bahasa Indonesia, Burmese, Hindi, and Nepali are increasingly visible alongside Chinese and Portuguese, and traces the post-1999 institutional decision to preserve semantic asymmetry as a deliberate governance strategy: bilingual street signs perform a “Luso-Chinese cosmopolitan” identity that is now economically indispensable to Macau’s tourism and gaming-led economy, institutionally aligned with the Macau Forum and the Portuguese-speaking Countries network, and politically differentiated from the colonial-era renaming strategies seen in Hong Kong and other formerly colonised cities. Drawing upon Shi-xu’s cultural discourse theory, the paper argues that Macau’s bilingual street names constitute a “transcultural cultural field” in which national power, local memory, and international image interact continuously, and that the post-1999 preservation of asymmetry is best understood as a technique of identity management rather than as a passive inheritance of colonial habit. By offering this interdisciplinary synthesis, the paper advances a comparative resource for the study of multilingual cities in the Global East and elsewhere where colonial, national, and local discourses continue to negotiate the urban landscape.