The study investigates availability and utilization of reference sources in academic libraries in Nigeria. It is undertaken as a descriptive survey research design. The population of the study is post graduate students in University of Port Harcourt, totalling 1,264. The simple random sampling technique was used to select the sample. The sample size is (118) post graduate students. Validation of the instrument was done by experts in guidance and counselling department. The reliability was done using cronbach alpha with reliability coefficient of 0.80. The researcher and two trained research assistants distributed the instruments. Mean (x) and standard deviation was used to answer the research questions while the z test was used to answer the hypothesis at 0.05 level of significance. The findings revealed that there is a significant difference between availability and utilization of reference sources in academic libraries. In conclusion all reference sources are available but not up to date and underutilized. The reference librarians need to create awareness of availability of reference sources and guide students for maximum utilization. It was recommended among others that librarians regularly update reference sources in order to make them relevant at all times.