This study ascertained the principals management support practices to promote teachers instructional improvement for sustainable development in secondary education in Anambra State. Two specific purposes were formulated and two research questions guided the study. The study adopted a descriptive survey design. The study was conducted in the six education zones in Anambra State namely: Aguata, Awka, Nnewi, Ogidi, Onitsha and Otuocha. The study population comprised 257 principals in public secondary schools in the six education of the State. No sampling was used due to the manageable size of the population. The instrument used for data collection is a structured 15 items researchers developed instrument titled; Principals Management Support Practices to Promote Teachers Instructional Improvement Questionnaire (PMSPTIIQ). The face validation of the instrument was established by three research experts. The Cronbach alpha was used to determine the reliability of the instrument. Coefficient value of 0.84 was obtained. Data were analyzed using mean and standard deviation. The findings of the study revealed among others that secondary school principals in Anambra State do not engage in instructional supervision practices of observing classroom instruction to ensure curriculum coverage, monitoring teachers compliance to school schedules, meeting regularly with teachers to discuss instructional challenges and providing feedback to teachers after class observation. The study also found out that secondary school principals do not engage in adequate motivational practices to promote teachers instructional improvement for sustainable development in secondary education in Anambra State. Based on the findings, it was recommended that school administrators should always engage in instructional supervision practices by observing classroom instruction to ensure curriculum coverage, monitoring teachers compliance to school schedules, meeting regularly with teachers to discuss instructional challenges and providing feedback to teachers after class observation among others. Conclusion was drawn.