This study investigated the use of Management Information Systems (MIS) in decision-making on long-term planning, short-term planning and budgeting in the South-West Nigerian Universities. The study used the descriptive research design of the survey type. Data were collected from a sample of 600 subjects consisting of 400 academic staff holding administrative staff positions and 200 senior administrative staff heading units using stratified random sampling technique. Data collected were analyzed using frequency counts, percentages, means, standard deviation and t-test statistics. The three hypotheses generated were tested at 0.05 level of significance. The study revealed that MIS was not adequately used in decision making process on long-term planning, short-term planning and budgeting. There was no significant difference between Federal and State universities in terms of the use of MIS for decision making on both long and short term planning. There was significant difference in the use of MIS for decision making on budgeting between Federal and State universities in favour of the Federal universities. It was recommended that the MIS units should be adequately financed and maintained to ensure a free flow of information and adequate use of MIS in decision-making on short-term and long-term planning as well as budgeting. (Contains 6 tables and 3 figures.)