This study aimed at investigating the effectiveness of Mobile Learning in developing oral fluency among preparatory students. The researcher adopted the Quasi-experimental design. The Participants of the study were 60 students enrolled in the first year prep pupils in Alexandria. The participants were selected from Smoha prep school for boys in Alexandria . The researcher designed oral activities based on mobile learning apps which were used in teaching the experimental group, while the traditional method was used in teaching the control one in the first term of the school year (2019-2020). A checklist was designed to identify the oral fluency skills required for the prep stage . An oral fluency test was designed by the researcher and used as a pre and posttest for the two groups. The data were analyzed statistically by using SPSS. Results of the two groups revealed a significant degree of improvement in the experimental group's oral fluency test as a whole. Whereas the improvement in pronunciation and fluency was lower than the improvement in vocabulary, grammar and comprehension.