OPAC refers to information retrieval system composed of database of bibliographic records describing the books and other materials owned by a library or library system. This study was undertaken to explore the awareness and utilization of Online Public Access Catalogue (OPAC) by undergraduate students in Federal University Dutsin-Ma Library, Katsina State. Investigation was carried out in respect of the level of awareness, purpose for utilizing OPAC, extent of utilization, extent of satisfaction and challenges of utilizing OPAC in FUDMA library. The study employed the cross-section survey research method which accommodates large population. There were a total of 3,124 undergraduate students in Federal University Dutsin-Ma, out of which 319 respondents were selected for the study using cluster and simple random sampling techniques. However, only 285 students completed and returned the questionnaires. The data collected were analysed using mean and standard deviation. The study revealed that undergraduate students were aware of some of the services provided by OPAC, which include how to link to some online database via library‟s OPAC and finding out whether needed material is available in the Library or not. The study equally revealed that they made use of OPAC for various purposes which include locating book and non-book materials in the Library and retrieving the call number of a book. This indicated that undergraduate students utilize the above services more than any other services Moreover, they derive satisfaction from locating of book and non-book materials, finding out whether needed materials is available in the Library or not and identifying books in a given subject. However, some of the challenges found were lack of full awareness, power outage and inadequate computers at the OPAC station of the Library. In view of the above findings the research recommends that the management of the Library should employ other means of promoting awareness such as including OPAC into library instruction module and incorporates library guide on the University website.