The advance of society and technological development have led governments to transform their public policies in various areas, with a particular focus on the education system. In this context, many countries have focused their efforts on raising educational quality standards, especially in the development of digital competencies. This has generated the need to modify school curricula, incorporating Computational Thinking (CT) in areas such as mathematics. Several researches highlight the importance of providing tools to teachers to design meaningful pedagogical strategies that integrate mathematical thinking with CP, implementing innovative teaching practices that favor the development of skills in students. In line with these demands, the present research aims to design an instrument for the observation of mathematics classes that incorporate the PC through the programming of robots, in order to guide teaching reflection. The study is situated within an interpretive paradigm, with a mixed approach, and validates the content from both a quantitative and qualitative perspective. In conclusion, the instrument designed has proven to be a useful tool to guide teacher reflection, as it is structured in six key dimensions and has been validated in terms of clarity, coherence and relevance. However, the need was identified to add additional items to improve the sufficiency of some dimensions. Finally, a second validation process is suggested to ensure its reliability and applicability in different educational contexts.