This study aims to search for the effect of Flipped Classroom/Education (FC) on academic success and retention of knowledge in EFL context and learner opinions about this new teaching approach. Research includes two groups studying at compulsory English preparation class in 2013-2014 academic year. The research employs a quasi-experimental method with a pre-test post-test control group design. The tests that were developed by the researcher were used to collect the quantitative data. Focus group interviews were carried out in order to collect personal opinions of students about FC and descriptive analysis were done on collected data. The test scores of experiment group taught through FC were higher than the control group taught through Traditional Education (TE) method and the difference was statistically significant. The rate of the positive comments on FC was 73.77% while the rate of negative comments was 17.39%.