This study determined the relationship between teaching competency and teaching mixed-ability among teachers in the Division of Tagum City. Specifically, it examined the extent of teaching competency in terms of pedagogy, facilitation, technology, and course administration, and the extent of teaching mixed-ability in terms of teaching and learning, students’ motivation, materials, and classroom management. A quantitative approach using a descriptive correlational design was employed. The respondents consisted of one hundred sixty (160) teachers, and data were gathered through validated survey questionnaires. Statistical tools such as weighted mean, standard deviation, Pearson product moment correlation, and multiple regression analysis were used to analyze the data at a 0.05 level of significance. The findings revealed that both teaching competency and teaching mixed-ability were at an extensive level, indicating that these practices were often evident among teachers. Results also showed a significant relationship between teaching competency and teaching mixed-ability, suggesting that higher competency led to better management of diverse classrooms. Regression analysis further indicated that all domains of teaching competency significantly predicted teaching mixed-ability, with pedagogy emerging as the strongest predictor. It was recommended that targeted professional development programs be implemented to enhance facilitation, course administration, and technology integration, and to strengthen teachers’ capacity to address diverse learner needs effectively.