This study examines the effectiveness of the University–Government–Kindergarten Collaboration (UGK) model in training early childhood teacher candidates (TCs), using the Education for Sustainable Development (ESD) framework to assess its role in enhancing TCs’ competencies. Data were collected through a survey of 210 TCs and in-depth interviews with 12 participants. The findings indicate a structural imbalance in UGK: while university–kindergarten collaboration shows some effectiveness, the lack of governmental leadership weakens tripartite synergy. From an ESD perspective, although UGK fosters basic collaborative skills, it does not systematically develop higher-order ESD competencies such as systems thinking, normative awareness, critical thinking, and strategic action. By shifting the focus from institutional to student experience, this study offers a new analytical framework for teacher education models. It concludes that optimizing UGK requires stronger governmental coordination, deeper university–kindergarten cooperation, and explicit integration of ESD core competencies throughout the training system.