The study examined the joint and relative impacts of elements of management by objectives on the administrative effectiveness of public secondary schools in Ibadan North Local Government. A descriptive survey design method was adopted. A sample of 472 (30% of the total population) respondents was selected through simple random sampling technique. Data were collected through impact of management by objectives scale (r=0.83) and administrative effectiveness questionnaire (r=0.76). Two hypotheses were tested and data analyzed through multiple regression analysis. The five elements of management by objectives which constituted the independent variable jointly predicted administrative effectiveness of the respondents (R=0.8954). Precisely, the predictors contributed 77% (adjusted R2 =0.7655) to the variance of the criterion variable. Also, each of the independent variable significantly (P<0.05) predicted the dependent variable. Based on the findings, it was recommended that management of secondary schools should integrate and adopt management by objectives principles and practices so as to facilitate administrative effectiveness of their schools.