Immersive Technology has dramatically changed the concept of teaching and learning. Its academic study is recent, so there is little to no background information that can explain how its stimuli and cognitive reactions can improve students' learning experiences. Therefore, this study set out to analyze the psychometric properties of a questionnaire to measure the stimuli and cognitive reactions inherent in Immersive Technology. Rigorous criteria were considered in the questionnaire's design and validation in order to achieve this objective: theoretical review, expert judgment, cognitive interview, pilot test, and exploratory and confirmatory factor analysis. The instrument was administered to 231 middle school students in Concepción, Chile. Participants responded to the instrument after observing and interacting with science content using augmented reality and virtual reality technologies. After conducting the analyses, a latent structure with a good fit for the data was obtained, consisting of 16 items that underlie the latent variables, interactivity, presence, and flow. The questionnaire, called TINMER, presents a satisfactory level of reliability (0.85). Guidelines for its use are discussed to deepen the potential of Immersive Technology in learning experiences.