This study focuses on the undergraduates’ attitude as correlates of their academic achievement in cataloguing and classification in library schools in Southern Nigeria. Cataloguing and classification courses are the heart and soul of librarianship but some undergraduates will avoid the courses if they are made optional courses in library schools. Cataloguing and classification are compulsory in library schools in Nigeria; students are expected to pass the courses before they graduate but it was observed that some students failed the courses and were not able to graduate. Two research questions and one hypothesis were used for the study. Survey research of correlational type was adopted for the study. Final year constituted the population of this study. Purposive sampling technique was used to select all the 550 final year undergraduates in library schools in Southern Nigeria. Questionnaire was the main instrument used to collect data in this study. Descriptive and inferential statistics were used to present the results of the research questions and hypothesis respectively. Findings from the study revealed that: 397out of 550 questionnaires were returned and found usable for the analysis; undergraduates in the library schools in Southern Nigeria had negative attitude (-1.30) towards cataloguing and classification; majority 261(65.7%) of the undergraduates’ academic achievement was at average level and there was significant correlation between attitude and classification. The following recommendations were made to improve undergraduates’ achievement in cataloguing and classification courses: students should have positive attitude towards cataloguing and classification in library schools in Nigeria; lecturers should encourage the undergraduates to have positive attitude towards cataloguing and classification with the use of student-centred teaching methods which may improve their academic achievement in the courses and cataloguing and classification laboratory should be provided in the library schools to balance theories with practical to improve the achievement of the undergraduates in cataloguing and classification courses.