In a bid to improve services to the satisfaction of customers, many organizations use suggestion box to elicit information from their customers, clients or patrons. Given the complexity of university library system, this study specifically explored the use of suggestion box for communication and promotion of public relation services in Usmanu Danfodiyo University Library, Sokoto. The study applied quantitative research method, using case study and descriptive research design. The study covered the Main Library and 18 other branches in the University. Using a purposeful sampling technique, a sample of 96 users' suggestions drawn from across the University were used. The study revealed that many suggestions were received by the library from users through the suggestion boxes provided for them within an experimental period of two years (2015 - 2016). These suggestions, which further influenced the actions or decisions of the library, centered mainly on the areas of reservation of seats, access to current serials collection, ICT facilities, security, and environmental condition, among others. Despite its effectiveness, however, the use of suggestion box has inherent shortcomings such as coordination, non-participation of majority of users, fake/false suggestions by users, amongst others. To this end, the study proffered some useful suggestions for improvement.