This document provides an editorial introduction and overview of a special issue focusing on research into collaborative learning enhanced by mobile technologies. It summarizes 9 research papers that examine how mobile devices and applications can support collaborative learning in both formal and informal educational settings. The introduction discusses the evolution of this research area and need for further studies combining key findings on social learning and new technologies. It previews each paper's contributions and concludes that further theoretical development and designed prototypes are needed to deepen understanding of mobile collaborative learning.