The inadequacy of annual budget system has in recent times forced many countries' government into search for a more appropriate framework that supports the reform of policy makers degree of planning, improves inter and intra-sectoral resource allocation by effectively prioritizing all expenditures and dedicating resources only to the most important activities as well as developing accuracy of revenue estimation. Medium term expenditure framework (MTEF) seems to be the framework that best meets these criteria. This research paper investigated the concept of MTEF and its relationship with budget effectiveness in Nigeria public sector. The study adopts a cross sectional survey research design. Six-point rating scaled structured questionnaire starting from highly ineffective to highly effective was used to elicit primary data from 258 selected members of the population which consists of senior staff of accounting, finance and internal audit department of federal Ministry of finance, Fiscal responsibility commission and CBN. The result shows that the MTEF positively and significantly correlates with budget process, sectoral planning, aggregate discipline and revenue estimation in Nigeria public sector. The study concluded that MTEF has influenced budget effectiveness by overcoming the shot sighted planning, irresponsible resource allocation, and has coordinated the linkage between policy, planning and budgeting which led to improved service delivery in Nigeria public sector.