This study aimed to develop the Metaconceptual Awareness and Regulation Scale (MARS) -- a self-report instrument for measuring the extent to which students realise, monitor, and evaluate their ideas. MARS consists of 10 items scored on a six-point Likert scale for two factors: metaconceptual awareness and metaconceptual regulation. A pilot study was conducted with 349 10th grade students while 338 11th grade students participated in the validation study. In order to test the two-factor structure of MARS, confirmatory factor analysis was employed with data from the validation study. Findings supported the two-factor structure of the MARS instrument. For further validity evidence, the relationship between students' metaconceptual awareness and regulation and their use of learning strategies were examined using canonical correlation analysis. A significant correlation was found between the factors of MARS and learning strategies. Research and practical applications of MARS by science education researchers and teachers are discussed.