The Education for Sustainable Development SDG4 underscores the critical role of quality education in empowering future educators to become active participants in building sustainable and equitable societies. This emphasizes the need for effective teaching methodologies and communication strategies to engage learners from diverse backgrounds. Thus, effective instructional communication is vital for successful classroom interaction. This study utilized APP mentoring and training strategy to assess its effectiveness in honing the instructional communication proficiency of the teaching interns. Specifically, this investigated the entry and exit instructional communication proficiency levels in terms of linguistic competence and linguistic performance, the significant difference in the teaching interns’ entry and exit linguistic competence and performance levels, and the proposed action plan as a result of the study. This study utilized convergent parallel mixed methods, in which the APP mentoring strategy was applied to the 20 BEED teaching interns in one of the leading teacher-education universities in Cebu. Findings showed that both the entry linguistic competence and performance of the BEED teaching interns under low levels, yet after the implementation of the APP mentoring strategy, the levels are elevated to “high.” The level of linguistic competence of the BEED teaching interns has substantially increased from 18.55 mean to 24.50 mean. An increase of 5.95 points in the mean has increased. Such an increase is considerable since they are more exposed to English as the target language during the mentoring process and provided with enhancement activities to improve their instructional communication skills. It was concluded that APPL mentoring strategy is effective and recommended for use not only to the BEED teaching interns but also to all who undergo teaching internships.