The objective of this study was to examine the influence of political-adminis- trative interface on leadership performance in the Ministry of Petroleum of the Republic of South Sudan. The study was guided by Leader Member Exchange Theory. The study adopted quantitative descriptive research design targeting 1973 employees working in the Ministry of Petroleum. The researcher adopted Yamane sampling formula to arrive at 333 employees as the sample size. The main data source was primary data collected using questionnaires and interviews. Descriptive statistics techniques were used to analyse quantitative data which include frequencies, percentages and mean. Regression analysis technique was used to analyse the inferential statistics and to test the set hypotheses. The findings were presented in the form of tables and figures. The study established significant influence of inter-organizational relations on leadership performance in the Ministry of Petroleum and assessed intervention strategies that could be adopted to improve public leadership effectiveness in the Ministry of Petroleum. The study further concluded that the poor leadership performance in the Ministry of Petroleum of the Republic of South Sudan was due to inter-organizational relations caused by ineffective organizational structures. The study recommends that the Ministry of Petroleum should enhance the institutional structures for improved leadership performance there should be checks and balances in the operation of the ministry to achieve the desired accountability. Such checks and balances will go a long achieving operation efficiency and optimum resource utilization.