Edmodo is a media of private micro-blogging service which can create an effective learning experience and allow students to exchange collective and individual feedback and responses. This article refers to an experimental study on the effectiveness of Edmodo media to teach writing at one of Senior Highschool in Bandar Lampung. The samples were two classes namely experimental class which was taught using Edmodo and control class which was taught without Edmodo. Each class was divided into two groups in which each consisted of students having high motivation and those having low motivation. To gain the data, two instruments were used namely writing test and motivation test. The data were analysed by using Multifactor Analysis of Variance ANOVA 2x2 and Tukey test. Before conducting the ANOVA test, pre-requisite test namely normality and homogeneity test were conducted. The findings of this research are: (1) Edmodo is more effective than Picture Series to teach writing; (2) The students with high motivation have better writing skill than those having low motivation; and (3) There is an interaction between teaching media and studentsâ motivation in teaching writing.