The purpose of this study was to develop an instrument for appraising educational apps in mathematics education. The instrument allows mathematics related apps to be analysed based on the three aspects of the TPACK (technological pedagogical content knowledge) model, namely, content, technology and pedagogy. Four sub-scales were created with the first one examining the app role according to the type of task promoted: explorative, productivity and/or instructive. The second sub-scale appraises the degree of cognitive involvement when a learner interacts with the app. The third and fourth sub-scale deals with general pedagogical and operational affordance. The instrument framework was piloted and subsequently trialled with ten school teachers and mathematics educators to ensure content validity. It was further endorsed with examples of educational apps currently available in the context of the secondary curriculum.