Abstract The purpose of the work is to study the principles of legality and justice in the practice of administrative proceedings of the Republic of Kazakhstan. For this, methods such as system and comparative analysis, logical analysis, deduction, induction, and formal-legal methods were used. During the implementation of the study, the significance, and role of legal principles in administrative justice in the Republic of Kazakhstan were investigated. After analysing the model of the transition of the countries of the former USSR to the system of administrative justice and the specifics of its implementation in Kazakhstan, it was concluded that the principles of legality and justice are legally fixed in the Administrative Procedure Code of the Republic of Kazakhstan. This article analyses the studies of both Kazakhstani and foreign scientists concerning the application of laws and principles in administrative proceedings. In addition, some aspects of improving the system of administrative justice in the context of legislative regulation of the application of legal principles are considered. The practical value of the results obtained is to provide recommendations that will have an impact on the activities of the administrative justice system of Kazakhstan and will allow it to be implemented more efficiently.