Background/purpose: Despite the rapid assimilation of generative artificial intelligence (GenAI) into education, and initial evidence suggesting its potential in language learning, rigorous empirical investigations into its efficacy for cultivating specific language skills remain limited. This study aimed to address this lacuna by examining the impact of guided chatbot interactions on English as a Foreign Language (EFL) learners' listening and writing skills. Materials/methods: A quasi-experimental design was employed, involving 93 undergraduates enrolled in mandatory EFL courses at a public university. Participants were randomly allocated to an experimental group (n=48), engaging in 10 weekly researcher-designed GenAI-mediated listening and writing activities, or a comparison group (n=45) following a traditional curriculum with optional chatbot use. Data were collected at three time points: pre-test, immediate posttest, and a delayed follow-up. Additionally, post-test qualitative reflections on chatbot use were garnered. Results: While both groups demonstrated improvement over time, the experimental group reached significantly greater gains in both listening and writing at the immediate post-test compared to the control group. However, these advantages were not maintained at the follow-up assessment. Thematic analysis revealed that students valued the personalized and immediate feedback offered by the chatbots, yet expressed concerns about inconsistent content quality, occasional repetition, and the need for clearer task structures. Conclusion: Overall, the findings suggest that targeted GenAI-mediated EFL activities can facilitate short-term improvements in listening and writing performance. Future research is advised to investigate approaches for sustaining these gains, optimizing content generation, and refining the user experience to better support second language learners' long-term development.