Abstract: The usage of mobile phones by university students is becoming more popular than ever before. This study sought to determine the comparative effects of mobile phone calls on social interaction of students at Catholic University of Eastern Africa and Catholic University of Zambia. The study employed the use of symbolic interaction theory that brings to light that meaning is attributed to things out of social interaction with them. Literature review is later presented on the key objectives of the study as well as a conceptual framework; linking the independent variables to the dependent variable in light of intervening variables. The study used the descriptive research design, which incorporates the use of questionnaires in collection of qualitative and quantitative data. The study target population was the students of the Catholic University of Eastern Africa and the Catholic University of Zambia, totaling to 2,913 students. The study applied simple random sampling where a total of 385 students were selected. The response rate was 80% of the sample, presenting 309 students. The research finding was that students from the Catholic University of Zambia spend more time on phone calls than students from The Catholic University of Eastern Africa. The finding led to the following recommendations: time spent on the phone calls should be regulated by the students themselves, the students should learn only to answer urgent calls and in class settings or discussion settings calls should be answered after one has excused himself or herself. Conclusion on the study is that mobile phone calls affect social interaction of students. Key Words: social interaction, calls, mobile phone use, student, university