This study analysed secondary school principals’ application of management by objective (MBO) in the management of personnel and instructional programmes in public secondary schools in Anambra State. Two research questions were answered and two null hypotheses were tested at 0.05. The descriptive survey design was adopted with a sample of 801 respondents made up of 129 principals and 672 teachers. A self-designed questionnaire titled “Application of Management by Objective in Management of Personnel and Instructional Programmes” (AMBOMPIP) was used for data collection. The instrument was validated by two experts in the field of educational management and one expert in the field of measurement and evaluation. Internal consistency coefficients of 0.75, 0.78 were obtained for the two sections of the instrument using Cronbach’s Alpha method. An overall reliability co-efficient of 0.77 was obtained for the entire questionnaire. Data were analyzed using mean for the research questions, and t-test for the hypotheses. The p-value was used to determine the significance of difference at 0.05 significant level. The result among others revealed that principals in Anambra State apply management by objective in personnel management and management of instructional programmes. The study recommended among others that the State government through the school boards are to consistently organize seminars and workshops for principals in order to update their knowledge of MBO so that they can utilize the benefits and apply it to various administrative areas of the school.