The purpose of this study is to investigate the extent of utilization of Quality Assurance Handbook in the supervision of instruction in secondary schools. Descriptive survey design was employed. The quantitative data were collected through an 18-item questionnaire titled, "Extent of Utilization of Quality Assurance Handbook in Secondary School Supervision of Instruction and Hindrance" (EUQAHSSSIH). This was administered to 210 supervisors made up of external and internal supervisors. Data were analyzed using mean and standard deviation for research questions and t-test statistics for the two hypotheses. Findings of the study revealed among others that both external and internal supervisors do not make adequate utilization of the Quality Assurance Handbook, in the supervision of instruction of secondary schools in Enugu State. It was also revealed that some factors which include unawareness of the supervisors about the existence of the Handbook contributed to its non-utilization. Based on the above some recommendations were made: such as making the Handbook available to principal in the schools.