This study aimed to (1) investigate students' mindsets before and after the growth mindset is instilled on them, (2) examine effects of growth mindset-based instruction on students' English learning behaviors, (3) explore effectiveness of growth mindset-based instruction on students' oral communication learning achievement, and (4) investigate students' attitudes towards their learning experiences through growth mindset-based instruction. The study was conducted with a sample group of 42 English majored undergraduate students who were enrolled in the English Discovery Course in the first semester of the academic year 2022 at Prince of Songkla University, Surat Thani Campus. The experiment was carried out once a week and lasted eight weeks. Data were collected using mindset test questionnaire to investigate students' mindset before and after the experiment and analyzed by employing descriptive statistic of mean and S.D. before administering oral communication pre-test and post-test. The scores from the pre-test and the post-test were compared using paired sample t-test and Hedges' g effect sizes to measure the effects and the magnitudes of effects caused by the treatment. Qualitative data were collected using a students' learning behavior checklist, a lecturer's observation form and a students' log. The study findings revealed a tendency of students' mindsets shift from fixed mindset to growth mindset. The data obtained from the students' behavior checklists and the lecturer's observation form exhibited students' productive learning behaviors during the experiment. A statistically significant difference between the mean scores of the oral communication pre-test and post-test was gained at a significance level of 0.01. The effect sizes calculated by means of Hedges' g yielded the value of 1.31 which was considered large. Also, students' positive attitudes could be perceived from the records in their logs. The findings suggested that growth mindset-based instruction could be implemented in an EFL class as it could yield positive effects on students' learning behaviors and improve their oral communication learning.