This study, determined the perceived management capacities of school principals for the effective implementation of the Universal Basic Education in junior secondary schools in South East Nigeria. To achieve this purpose, six specific objectives and six corresponding research questions were formulated to guide the study. The descriptive survey research design was employed for the study. The population of the study comprised all the principals and teachers in public secondary schools in five states of Abia, Anambra, Ebonyi, Enugu and Imo states in south east geopolitical zone. The sample of the study was 1239, made up of 162 principals and 1077 teachers drawn from three states of Anambra, Eboni and Enugu states using proportionate simple random sampling techniques. The research instrument used to collect data for the study was questionnaire (Perceived Management Capacity Assessment Questionnaire). Five experts validated the instrument. Crombach Alpha reliability method was used to determine the internal consistency of the PMCAQ items which gave Alpha reliability coefficient of 0.89. The data collected were analyzed using mean and standard deviation to answer the research questions. It was found out that school principals require 16 capacities in instructional leadership, 12 capacities in staff personnel, 14 capacities in student personnel, 10 capacities in school plant, 10 capacities in school finance and 12 capacities in school-community relations management for the effective implementation of the UBE programme in junior secondary schools in South East, Nigeria. Based on the findings, it was recommended that Government and her agencies in charge of education administration should sponsor and encourage school principals to attend and compulsorily participate in re-training programmes, like workshops, seminars, symposia, among others to acquire the required capacities for the effective implementation of the UBE programme. Principals of secondary schools should utilize the findings of the study to seek for avenues to improve themselves through collaboration and other capacity building re-training strategies to acquire the required capacities for better service delivery. Curriculum planners should incorporate the findings of this study in the curriculum of teacher education so that the would-be schools principals will be well grounded in capacities required for the effective implementation of educational programmes.