The success of the project depends on the quality of management, in particular, the management methodology chosen for the project. When it comes to developing new software, the development team and the customer are faced with the methodology choice and approach to the development of this software. The purpose of this work is to explore and analyze two completely different approaches to software development – the traditional (Waterfall) and the flexible (Agile). In the article are described implementation principles, advantages, and disadvantages of traditional (Waterfall) and flexible (Agile) methodology. It is made an emphasis on using these methodologies on real projects are made. Also, we analyzed the so-called “Project Management Triangle” and its role in project formation using different management methodologies. A visual representation of the software development process using these two methodologies was embedded to better understanding the specifics of each. During the analysis, conclusions were made regarding the relevance of methodologies in a modern, dynamic environment. Detailed description and analyze of Manifesto of Flexible Software Development, which changed people's perception of the process of developing and creating new projects not only in the field of IT but also in all other spheres of life, were conducted. As a result, were made conclusions about the inability of traditional methodologies (including the Waterfall model) to meet modern market requirements and was preferred Agile methodology, which enables customer requirements to be met in a dynamic environment, ready to changes and promote them.