This study examines the relationship between instructional supervisory skills and teacher performance in the school setting, with particular emphasis on analyzing the role of technical assistance and mentoring capacity. Specifically, the study aims to determine how supervisory skills of instructional supervisors influence teacher performance and how technical assistance and mentoring capacity contribute to strengthening or supporting this relationship to enhance teachers’ professional effectiveness. This study employed a quantitative descriptive–correlational research design. This design was used to systematically describe the status of the variables and to determine the relationship between instructional supervisory skills, technical assistance, mentoring capacity, and teacher performance. Data were analyzed using descriptive statistics, correlation analysis, mediation and moderation tests. Results revealed that instructional supervisory skills, technical assistance, mentoring capacity, and teacher performance were all at very high levels. Significant positive relationships were found between instructional supervisory skills and teacher performance, instructional supervisory skills and technical assistance, and technical assistance and teacher performance. Technical assistance partially mediated the relationship between instructional supervisory skills and teacher performance. However, mentoring capacity did not significantly moderate the relationships among the variables. The combined influence of instructional supervisory skills, technical assistance, and mentoring capacity significantly affected teacher performance.