Technology mapping ™ is proposed as an approach for developing technological pedagogical content knowledge (TPCK). The study discusses in detail instructional design guidelines in relation to the enactment of TM, and reports on empirical findings from a study with 72 pre-service primary teachers within the context of teaching them how to teach with Excel. Repeated Measures MANOVA findings showed that TM was effective and efficient in developing TPCK competencies; however, development of TPCK competencies was directly related to the complexity of the design task, as this was determined by the educational affordances of Excel.