The article examines the actual problem associated, on the one hand, with increasing requirements for the flexibility of human resources and management systems in conditions of increased dynamism and uncertainty of environmental factors, and, on the other hand, with the lack of scientifically based and practical approaches to assessing the flexibility of human resources with its subsequent formation. The relevance of flexibility is enhanced in relation to the human resources of innovative project teams, which are characterized by an even higher level of uncertainty, unpredictability and variability of project environment factors. This determined the purpose of the study, which is formulated as the development of a methodological approach to assessing the flexibility of human resources of innovative projects. To achieve this goal, there were set tasks of defining the concept of flexibility of human resources of projects, flexibility criteria and principles of their evaluation. The author used methods of analyzing the provisions set out in scientific publications, as well as the method of expert survey, which helped to formulate the hypotheses of the study, and then test them in practice. Using this method, 155 project managers and specialists from 36 enterprises in Russian cities were involved in the study. All enterprises implement innovative projects. The main conclusions of the expert survey were the following: innovative projects require flexible staff, flexibility is reduced to the ability to quickly and efficiently update their competencies, enterprises need methods for evaluating and developing the flexibility of human resources in projects, staff flexibility can be provided with a flexible management system. These findings became the basis for the development of a methodological approach to the assessment of flexibility, which provides for the assessment of the flexibility of people in projects and the assessment of the flexibility of project human resource management. There were proposed criteria for assessing flexibility, which are related to the assessment of the speed, depth and scale of updating the competencies of human resources of projects. The proposed developments can be useful to project managers for their activities to ensure the flexibility of innovative projects and people in these projects.