Role-play is a natural and dominant form of early childhood activity. While playing, a child masters new forms of behavior, learns to interact with others, and develops imagination and self-regulation skills. The existing methods of play assessment are based on different theoretical approaches that variously define both the criteria for play and the role of play in the children's development. Yet, none of these methods consider play in view of its developmental potential or from the perspective of a particular playing child, including the level of engagement in the play situation. This article introduces a tool for observing and evaluating play which has been designed within the framework of the cultural-historical approach. The Play Matrix allows observers to track 22 behavioral variables, clustered into three categories: actions, verbal actions, and emotional manifestations. The article discusses the theoretical foundations for creating this Matrix, and describes in detail its structure and techniques for its use. Examples of the play analysis using the Play Matrix are given.