This study examined mobile phone apps and the utilization of library services in university of Calabar library, Nigeria. Four objectives and four hypotheses were formulated to guide the study. Survey research design was used. The population of the study constituted of all registered library users in the 2015/2016 academic session. The population was 4,265 registered users. A sample of 225 registered users was selected using purposive and accidental sampling techniques. Questionnaire was the instrument used for data collection. Pearson product moment correlation analysis was employed to test the hypotheses at .05 level of significance. The findings revealed that there was a significant relationship between Tweeter apps and the utilization of library services, (r=0.57*, P<.05, df=223, rcritical=.138); there was a significant relationship between Whatsapp and the utilization of library services, (r=0.47*, P<.05, df=223, r-critical=.138); there is a significant relationship between Facebook apps and the utilization of library services, (r=0.59 ⃰ , P<.05,df=223,r-critical=.138); and there is a significant relationship between Skype apps and the utilization of library services, (r=0.51⃰ , P<.0.5, df=223, r-critical=.138). From the result of the study, it was recommended among others that the use of mobile phone apps as communication infrastructure should be encouraged in the University of Calabar Library.