This study aimed to develop the Lifelong Learning City Self-Assessment Toolkit that can be used for local governments to autonomously evaluate and diagnose their performance as learning cities while reflecting the characteristics of the Korean lifelong learning city. The literature informed the initial development of learning city indicators; the initial indicators were, then, examined and subsequently validated by researchers and field experts in lifelong learning cities through focus group interviews over multiple stages. The final learning city assessment toolkit comprises a basic module, a subject module, and a performance module. The basic module is an indicator for the construction of a lifelong learning city base and the vitalization of lifelong learning. The topic module is a specific module for each subject. The subject module is a specialized module for each local government and consists of seven types: learning-as-culture type, whole community as-learning-sites type, learning-as-empowerment-and-mobilization type, learning for economic vitality type, learning-for-all type, learning with urban renewal type, and community school type. Finally, the outcome module is divided into two sections: lifelong learning outcomes and urban growth outcomes. Each module would be autonomously combined by local governments and configured to be utilized in accordance with the regional features and vision of a learning city. Based on the results of this study, The advantages and application of this Lifelong Learning City Self-Assessment Toolkit for self-evaluation and diagnosis of learning cities were discussed.