The increasing popularity of mobile dual-language learning applications (apps) in the education industry has led to a growing interest in investigating their effectiveness. However, there is a paucity of research investigating mobile apps specifically designed for speakers learning dual languages. Accordingly, this study utilised a qualitative research method to explore the perceptions and design of such apps for bilingual teaching and learning. A cohort of 30 in-service teachers participated in individual interviews, serving as the primary source of data collection and analysis. Thematic analysis was employed to identify patterns within the transcripts and detailed field notes. The results revealed nine themes and twenty-four subthemes related to mobile dual-language learning apps. These findings provide insights into the potential benefits and challenges of using mobile apps for language learning, as well as implications for the design of dual-language learning apps. The implications of this study extend beyond the education industry and have practical implications for language educators and app designers alike. The study contributes to the current body of knowledge in the field of education by shedding light on the effectiveness of mobile dual-language learning apps for bilingual teaching and learning.