This study investigated headteachers instructional supervisory practices and teachers job performance in GaEast Municipality, Ghana. This study employed descriptive survey design with quantitative approach where through census and proportionate stratified random sampling techniques, a sample of 195 comprising 65 headteachers and 130 teachers were respectively selected from seven circuits. Having satisfied the validity and reliability requirements, quantitative data was analysed using both descriptive and inferential statistic with the aid of Statistical Product for Service Solutions (SPSS) version 26. The finding revealed that the headteachers practiced all the instructional supervision dimensions outlined in this study, however, the headteachers mostly practiced checking teachers' professional records while conducting classroom observation was least practiced. The study established that the level of the teachers’ general job performance as well as the various dimensions of job performance was very good, however, the teachers’ level of job performance was highest in relation to their management skills and lowest on their teaching skills. The study indicated that the job performance of the teachers was linked to the instructional supervisory practices of the headteachers. Based on these findings it was recommended that the Ghana Education Service through the Ga-East Municipal Education Directorate should organize in-service training for the headteachers to equip them with relevant competences in the practice of instructional supervision in the schools, especially in conducting classroom observation the provision of instructional resources. It was also recommended that education stakeholders in the Ga-East Municipality should support the teachers to sustain this level of performance and improve on it so to realize educational goals in the municipality.