<p>This study investigates the effectiveness of AI-mediated informal digital learning in enhancing oral English competence among Chinese English majors. Employing a mixed-methods research design, the study combines quantitative and qualitative approaches to assess the impact of AI tools on students’ oral proficiency. A quasi-experimental design was used, with 90 undergraduate participants divided into an experimental group, which engaged with AI-based learning platforms, and a control group, which relied on traditional self-study methods. The results reveal that the experimental group demonstrated statistically significant improvements in oral English skills, indicating that a structured AI-supported out-of-class speaking program combining repeated speaking practice, interaction, and feedback may support the development of oral proficiency and learner autonomy. Additionally, thematic analysis of semi-structured interviews with participants highlighted positive experiences, including increased confidence, engagement, and perceived improvements in pronunciation and fluency. These findings suggest that AI-mediated informal digital learning can function as an effective supplementary practice environment for oral English development outside the classroom. The study acknowledges limitations, such as the sample size and the short duration of the intervention, and provides recommendations for future research to explore the long-term effects and pedagogical integration of AI in language learning.</p>