The purpose of this study is to develop a multi-dimensional scale to measure students' awareness of key competencies for M-learning and to test its reliability and validity. The Key Competencies of Mobile Learning Scale (KCMLS) was determined via confirmatory factor analysis to have four dimensions: team collaboration, creative thinking, critical thinking and problem solving, and communication. The research subjects are 815 students from the elementary school that participate in M-learning programme in Taiwan. The research results show that students have better self-awareness in team collaboration and creative thinking, but have worse self-awareness in critical thinking and problem solving. This study also found that there was no significant difference between genders in the KCMLS, but students who study in the schools that committed in M-learning longer have higher awareness in all dimensions than students who study in the schools that committed to M-learning in fewer years.