ABSTRACT Local Agenda 21 is broadly recognized as a tool for sustainable development at municipalities with more than fifteen years of experiences worldwide. However, it has to be assumed that many of these local processes do not reach the expected results as they extinguish or hardly continue very few years after their beginning. Assuming complexity and uncertainty of development processes, this research has focused on how planning approach influences the way LA21 contributes to democratic governance for sustainable human development at the local level. Particularly, the methodology developed by UN/HABITAT and PNUMA programmes, Localizing Agenda 21 and Sustainable Cities Programme, has been analyzed through a qualitative research. Main contributions of the research are the following ones: 1) a holistic model describing the influence of the different factors in LA21 success, 2) an analytical framework for understanding the relation between democratic governance and LA21 processes, 3) methodological guidelines to improve LA21 from a practical point of view. Conclusions of the research highlight the necessity of understanding human sustainable development as an integral and holistic issue by overcoming environmental biases. Conceive LA21 as a tool for sustainable human development requires to include spaces, instruments and conditions for deliberative processes within methodological approaches. In addition, it is required for LA21 initiatives to adopt a process approach in order to truly contribute to democratic governance for sustainable human development. This needs deepening the participatory and accountability dimensions of governance. Finally, it is important to recognize the influence of international cooperation in LA21 processes in developing countries. The very nature and arquitecture of LA21 methodologies and their particular approach and implementation are strongly influenced by international agenda and institutions.