Military culture involving, for example, a lack of autonomy and hierarchical structure, has hindered Taiwanese military students' English learning and increased the difficulty to obtaining learning materials. In particular, English for specific purposes (ESP) vocabulary learning is difficult for military students when English is used as a medium of instruction. Mobile technology can be adopted to assist such students in learning ESP vocabulary. However, studies on this topic are limited. Therefore, the present study investigated military students' acceptance of mobile-assisted engineering vocabulary learning. We recruited 45 military students to complete a 4-week mobile-assisted engineering vocabulary learning task using Quizlet. A questionnaire was administered, and their responses were analysed using partial least squares structural equation modelling. The results revealed that system characteristics positively influenced the perceived ease of use and perceived usefulness of Quizlet. Perceived usefulness positively influenced behavioural intention through attitude towards use. However, perceived ease of use did not significantly influence perceived usefulness or attitude towards use because of the limited convenience of studying at the military base. App developers and teachers should consider military students when designing apps and make design choices to maximise the ease of use of their apps outside of the classroom. The present study provides insight into mobile-assisted ESP vocabulary learning.