The study investigated the integrity and job performance of some selected federal university libraries in South-South, Nigeria. The study adopted a descriptive study. The population of the study consist of 118 librarians. 118 librarians were distributed, and only 95 copies of the questionnaire were retrieved using descriptive statistics mean and percentage mean score of 2.5 and above and percentage score of 50%. The study revealed that the integrity traits of librarians in the university libraries under study are honesty, trust, dependability, sound judgement, wisdom and unbiased. The study further revealed the following as effects on integrity traits on the job performance of librarians as: to become a reliable organization, good reputation, rapid development, improve services, smart decisions and reduce employee turnover respectively. The study recommends that libraries should recruit librarians with a good history of integrity traits and also the library management should sponsor librarians to regular seminars/workshops on integrity or similar topics for rapid development and to improve library services.