Background: Metacognition is a multi-facet psychological construct; deficits in metacognitive abilities are associated to low social functioning, low quality of life, psychopathology, and symptoms. The aim of this study was to describe and develop a valid and reliable interview for assessing metacognition. Methods: The semi-structured interview, based on the author’s theory model of the metacognition construct, is described. The Metacognition Assessment Interview (MAI) is an adaptation of the Metacognition Assessment Scale(MAS) and evaluates how the subject is interviewed used metacognition during his own real life experiences elicited by the interviewer. A user manual was developed to assist the interview and scoring procedure. Results: Exploratory factor analysis and confirmatory factor analysis revealed preliminary evidence of a two factor-hierarchical structure, with two lower-order scales, representing the two main theoretical domains of the metacognitive function, ‘‘the Self’ ’and ‘‘the Other’’, and one single higher-order scale that we labelled metacognition. Contrary to the authors’ prediction the existence of the four distinct dimensions under the two domains was not confirmed. The MAI and its two domains demonstrated acceptable levels of inter-rater reliability and internal consistency. Conclusions: The MAI appears to be a promising instrument for assessing metacognition. Future psychometric validation steps and clinical directions are discussed.