Existing studies have evidenced that mobile-assisted vocabulary learning, which allows students to create artefacts and engage in productive skills, can help them in vocabulary learning. However, there remains little research and validated approaches for designing seamless vocabulary learning experiences for young learners. In this paper, a seamless vocabulary learning system was specifically designed for young learners. The study involved three classes of primary 2 students to investigate the learning effectiveness of seamless vocabulary learning, with a focus on analyzing student-generated artefacts. The results validated the effectiveness of seamless vocabulary learning for young learners, emphasizing the importance of strengthening the connection between home-based learning and classroom-based learning. The study also indicated the pivotal role of providing students with opportunities to improve their artefacts constantly across different learning contexts.