The present study aimed at investigating the effect of using Mind mapping technique in improving EFL first year secondary stage students' English grammatical achievement. The instrument that were designed and used in the current study were an English Grammar Achievement test used as pre, post and follow- up test to measure students' grammatical achievement level and a questionnaire related to English grammar learning problems to identify the difficulties the EFL first year secondary stage students have in English grammar learning and achievement. The study adopted the experimental design using one group. The participant of the study consisted of thirty students selected from first year secondary stage of Ghazala Secondary School, Sinbillawin, Dakahlia governorate during the first semester of the academic year 2013-2014. The participants were taught using Mind Mapping technique. The collected data were analyzed and treated statistically using SPSS. Results provided evidence to the effectiveness of using Mind Mapping technique in improving the students' English grammar achievement. A number of recommendations concerning the use Mind Maps, English grammar learning and teaching, and course design were suggested. Key Words: Electronic Mind Maps, English grammar, EFL, Achievement, Secondary stage students.