E-learning is an important trend globally that is believed to enhance the acquisition of knowledge by students within and outside the classroom to improve their academic pursuit. The Online Discussion Forum (ODF) is one of the tools that are used for e-learning in Nigerian universities. It facilitates interaction among postgraduate students as they can communicate and share information sources with one another to promote learning. However, the optimum use of this forum is determined by anchor factors in TAM 3 such as computer self-efficacy, perceptions of external control, computer anxiety and computer playfulness. A conceptual model based on TAM 3 was proposed and empirically tested. Using a survey research design and an online questionnaire for 121 Library and Information Science (LIS) postgraduate students, the paper demonstrated that computer self-efficacy, perceptions of external control, computer anxiety and computer playfulness have significant influence on the use of ODF.