The purpose of the article is to substantiate the unified theory of urban shrinkage based on heterodox economic approaches, which will overcome the dominant neoclassical paradigm with its reductionist explanations and one-sided normative guidance. Research methodology is a qualitative meta-analysis of heterodox studies of regional/urban economics (including institutional, evolutionary, behavioral economics, discursive institutionalism, narrative economics, place marketing and place branding, and generational theory) and identification of the potential for integrating these approaches into a single theoretical framework. Research objectives: a qualitative assessment of the theoretical basis of urban anti-shrinkage policy used in practice; analysis of advances of heterodox theories in the field of urban economics; analysis of areas of intersection and prospects for the formation of a joint research program. The article presents a new approach, complexity-focused institutional economics, which can become a methodological basis for the formation of a heterodox urban-shrinkage theory. The main findings of the study are to substantiate the potential directions of heterodox synthesis in urban shrinkage studies, as well as to present a complexity-focused methodology and interdisciplinary framework for analyzing shrinking cities.