This study examined determinants of library and information science undergraduate students' first impression with the university library websites. A total enumeration method was used to involve 54 year 4 undergraduate students of Library and Information Science from two selected universities. Undergraduate Students' Determinants of First Impression with University Library Websites Questionnaire was used to gather data. The results obtained demonstrate that there is significant correlation between LIS students' Perception of Website quality, Website interactivity, Website aesthetic perception, Website prototypicality, and Website satisfaction with first impression toward the university library website. The five independent variables (Website quality, Website interactivity, Website aesthetic perception, Website prototypicality, and Website satisfaction) jointly (as indicated by the R-square value) explained or predicted 66% of the variation in LIS students' first impression towards university library website. Aesthetic perception of library website contributed most to the prediction of LIS students' first impression towards library website, followed in declining order of strength by library website interactivity, library website satisfaction, and library website quality. However, prototypicality though correlated with first impression, its contribution is not significant. Notable limitation of this study is that, data was collected from undergraduate students in only two universities focusing only Library and Information Science students. The results call for formidable efforts to improve the users experience on the web, because the first impression counts. This study has implications for the users patronizing the university library websites. The results show that Aesthetic perception of library website contributed mostly to the prediction of LIS students' first impression towards university library website, followed by library website interactivity. These findings may not be applicable to other university library websites but this depend on the experience of the users.