Copying words by writing and typing are two effective methods in traditional learning, but their merits for learning L2 words have seldom been compared. Because of technological advances and the growing popularity of utilising smart mobile products to acquire L2 vocabulary, this study investigated the effectiveness of writing and typing techniques in increasing L2 word acquisition in a mobile-assisted environment and compared their impacts on learning outcomes. Both methods were found to help learners achieve better performances than the control condition, but their advantages differed. Writing improved both immediate and delayed learning, whereas typing only helped with longer-term learning. Based on these findings, people who teach or learn L2 vocabulary in either conventional fixed settings or mobile-assisted environments are encouraged to employ both writing and typing approaches. Programmers are also suggested to integrate the two approaches in their future development of vocabulary learning apps on smart portable devices.