The objective of this study is to examine the effects of mobile phone use on the study habits of University of Karachi students. The research was carried out using questionnaires distributed to 1200 students who own mobile phones .The questionnaires collected demographic information about the respondents, mobile phone type preferences, uses of mobile phones during study, predominant usage during study and information about challenges facing students in using mobile phones for study purposes. The results showed significant gender differences in several aspects of mobile phone use. The results also revealed that mobile phone use has negative and positive effects on the study habits of university students depending on usage patterns.