This study investigated Principals’ Leadership Behaviours as correlates of Students’ Academic Performance in Public Senior Secondary Schools in South-South, Nigeria. Five research questions and five null hypotheses were raised to guide the study. Correlational survey design and ex-post facto design were adopted for the study. From a population of 84,841 teachers and 709 public senior secondary schools, a sample size of 382 teachers and 71 public senior secondary schools in Edo and Delta States in the SouthSouth, Nigeria was taken using multistage sampling technique. Two instruments titled ―Principals’Leadership Behaviour Questionnaire (PLBQ)‖,and ―Students’ Academic Performance Proforma (SAPP)‖ were used to elicit data for the study. The reliability of the PLBW was determined using split half method and correlated using Pearson product moment correlation which yielded reliability index of 0.82.Descriptive and inferential statistical tools were employed for the analysis of data. Research questions were answered using mean scores and standard deviation; while the null hypotheses were tested at 0.05 level of significance using linear regression and multiple regression analysis. The findings of the study revealed that task centred, people centred, transformational and transactional leadership behaviours were exhibited by school principals; there is a high extent of teachers’ continuing professional development; and a very good performance in SSCE results in public senior secondary schools in South-South of Nigeria from 2013 to 2022. The study concluded that there is significant relationship between principals’ leadership behaviours and students’ academic performance in public senior secondary schools in South-South of Nigeria. Based on the findings and conclusion, it was recommended among others that principals should critically identify and continuously demonstrate leadership behaviours that enhance their administrative competences and facilitate satisfactory academic outcomes of secondary school students in South-South of Nigeria