The study is a survey research intended to find out undergraduate usage of mobile phones and its implication of school application. The colloquium population is 27,650 at which two hundred and thirty-eight undergraduate students were randomly selected from two universities in the Federal Republic of Nigeria. A questionnaire on "current trends in mobile phone usage among adolescents" was used for the study. The instrument was validated and tested reliable. Five research questions were formulated to guide the study. The researcher as well as ten research assistants personally administered the questionnaire. The questionnaire forms were collected on the spot and so there was a hundred percent rate of return. It was discovered that nearly all the undergraduate students own mobile phones and the majority consider it very useful. Several reasons were advanced for owning a mobile phone by students. These include: for mobility, emergency, e-mails and short message service, self assurance, improved social status, for fashion, loading information, social network and malpractice. The features commonly used by students apart from sending and receiving calls is the short message service. The implications of mobile phone usage by students on school administration are: it is an object of distraction, encourages laziness as students now browse instead of going to the library, an object for examination malpractice and several other vices. Recommendations were made to check the use of mobile phones by undergraduate students in Nigerian universities.