This paper examines the current mobile vocabulary learning practice to discover how far mobile devices are being used to support vocabulary learning. An activity-centered perspective is undertaken, with the consideration of new practice against existing theories of learning activities including behaviorist activities, constructivist activities, situated activities, collaborative activities and informal and lifelong activities. Such an approach allows one to reflect on the advantages of L2 vocabulary learning and to hypothesize what features of this technology are likely to change language teaching and learning. The integration of mobile devices and vocabulary learning needs to take into consideration portability, social interactivity, context sensitivity, connectivity and individuality. Insights gained from the categorization of activity type will inform researchers and teachers of the emerging vocabulary learning practice and its potential relevance to the innovation in language language teaching and learning.