This study explores critical incidents regarding differing cultures-of-use in telecollaboration against the backdrop of Hong Kong and German teacher education contexts. The rationale for the exchange was to model technology use and task design with the ultimate goal of internationalizing teacher education and supporting global citizenship. Participants in this project are 58 English majors in a graduate-level sociolinguistics course at a public research institution in Hong Kong and 15 EFL student teachers in a language teaching and new media elective course at a public education university in Germany. Using social media tools for interaction such as Facebook, Skype, WeChat, and WhatsApp, 11 telecollaborative teams engaged in three sequential tasks: (a) engaging in topical exchanges using Facebook, (b) writing a literature review in Google Docs, and (c) making recommendations on team websites using Wix. Research questions focus on critical incidents identified by participants during these tasks, particularly in relation to tool engagement. Data triangulation includes reflections, surveys, and online interactions. Findings indicate that the majority of Hong Kong teams cite low experience with certain tools, unfamiliarity with alternative tools (e.g., WeChat), and differences in tool access and use as constraints in achieving effective communication. Implications address sensitizing participants to their partners' tool socialization through implementing the critical incident technique.