The study was designed to investigate how information system IS measures (such as system quality, information quality, service quality, technological/infrastructural issues, users’ IT self-efficacy) influence user satisfaction of the university of Ibadan postgraduate school portal using a conceptual model adapted from Delone and McLean (2003). A descriptive survey was employed as the research design in the study. The literature review covered information system IS, web portal and User satisfaction. Self-structured questionnaires based on the adapted model were administered as data collection instrument. A sample size of 385 students was drawn and same copies of questionnaire were distributed proportionally to postgraduate students across the 19 faculties of the postgraduate school. The data was analysed using descriptive and inferential statistics. The web portal initiative is a good step in the right direction and will subsequently yield greater dividend and better user satisfaction for it users if some of the impeding factors to user satisfaction were adequately addressed. The result shows that system quality (.000), information quality (.008), service quality (.000) and infrastructural issues (.031) were significant predictors of users satisfaction, however, none of the IS measures predicted favorable on users’ IT self-efficacy. The study further concludes and recommended that the stakeholders in the university should implements an effective IT policy that would instil the efficient management of the postgraduate school web portal in addition to large scale investment in internet infrastructure for maximum user satisfaction. Further studies could focus on using other information systems model to measure user satisfaction.