The study focuses on the use of reference sources and services by students in ACE Library, Ondo, Ondo State, Nigeria. Reference sources are materials in the reference section while reference services are rendered by reference librarian in meeting the information need of users in the library. The study surveyed 405 students comprising 183 and 222 Degree and NCE students respectively from the five schools in the College. Questionnaire was used to collect data. All the 405 questionnaires that were administered were returned and found valid for analysis. The findings of the study among others show that 246(60.7%) had good understanding of what reference materials are; 222 (54.8%) have good understanding of what reference service entails and 295(72.8%) make use of reference materials in the College Library. The major challenges confronting the students in the use of reference materials include very old materials 82 (20.2%) and time wastage when searching for materials 75 (18.5%). It could be concluded that students make use of reference materials and have understanding of reference sources and services probably because both the Degree and NCE students have compulsory courses in Library Instruction Programme and Introduction to Library Studies respectively. From findings of the study, it could be recommended that new reference materials should be acquired to cover all courses and reference librarian should organise orientation for the students on the use of reference materials in the library.