Teacher perspectives have been lacking in the mobile-assisted language learning (MALL) literature. To fill this gap, this study investigates how Chinese teachers implemented WeChat-supported language tasks and the challenges they encountered in the process. Based on technology-mediated task-based language teaching and authentic assessment frameworks, we designed tasks that aimed to achieve both pedagogical goals (focusing on linguistic forms and achieving authenticity) and technological goals. Teachers' reflective journals revealed that implementing WeChat-supported tasks was a holistic and dynamic process, entailing four interrelated phases and requiring continuous management of unexpected events. This indicates that teachers should develop new skills and play complex, well-rounded roles to meet both the pedagogical and technological goals of technology-mediated tasks in MALL in the digital era.