T he present study aimed at investigating the effectiveness of MI- based activities in developing the speaking skill of a sample of first year secondary students . The quasi- experimental design was used for conducting this research .A group of sixty 1st year secondary students were randomly selected from one of Cairo governmental secondary schools, namely El – Salam Secondary School for Girls, in the school year 2014-2015 (30 students in the experimental group and 30 students in the control group) . The instruments of the study were : 1) A speaking skills list ;  2)A speaking  pre-posttest and 3) AMI – Inventory and 4) A speaking performance scoring rubric. Reliability and validity of the instruments were verified. The experiment lasted for three months in the second semester of the academic year 2014/2015 .Results of the study indicated that the MI- based activities proved to be effective in developing the target speaking skills , namely;interacting and managing conversation effectively, following grammatical rules accurately ,using relevant, adequate and appropriate range of words and word collocations, speaking fluently and demonstrating intelligible pronunciation . Based on the findings, a set of recommendations and suggestions for further research were highlighted.