This paper reports on the development of the "MobLearn@Work" App, which emerged from a study of informal learning among five employees at different companies in China. The purpose of the study was to develop a strategy for the design of mobile learning support tools that would enhance informal learning in the workplace. The App was developed by creating a platform to support informal learning through the integration of two sets of issues that emerged in the study: (a) affordances of contemporary Web 2.0 tools identified from the literature and by exploration of the participants' mobile technology uses, and (b) informal learning activities of the participants that emerged in the context of their work. Consideration of these issues led to the conclusion that an effective App for informal learning should include functionalities such as really simple syndication, podcasting, Web-searching and microblogging, all of which were integrated into the "MobLearn@Work" App. The implementation of the App in these five cases over a six-month period yielded a further set of design recommendations, which are discussed in the paper.