The present study sought to investigate the effect of using Edmodo, a Web 2.0 tool, as a supportive blended learning tool in developing EFL Saudi students' paragraph writing skills at Prince Sattam bin Abdul Aziz University, KSA. Eighty students majoring in English at the college level one participated in the study. The participants were randomly selected for an experimental group (taught by using Edmodo) and a control group (taught without using Edmodo). Two main tools were devised to collect data: Oxford Placement Test (OPT) and Test of Paragraph Writing Skills (TPWS). The data were analyzed descriptively and inferentially by running a t-test, using SPSS 16.0, to calculate the differences between the mean scores of the two groups pre- and post-intervention. The results showed statistically significant differences in the post-test in favor of the experimental group. Integrating Edmodo into the writing class was found to be highly beneficial in developing EFL students' writing abilities, up to paragraph level. The use of Edmodo also enriched students' knowledge and increased their motivation to learn.