Web 2.0 technologies have become an integral part of our lives, transforming not only how we communicate with others, but also how language is taught and learned in the L2 classroom. Several studies have looked into the use of these tools and how they influence L2 learning (e.g. Jin, 2015; Wang & Vásquez, 2014), yet only one has compared the effects of two Web 2.0 technologies (Castaneda Vise, 2008). Thus, the aim of this study was to compare the impact that Facebook and blogs had on the writing skills, namely, writing fluency, lexical richness, and syntactic complexity, of Japanese EFL learners. Moreover, the authors examined the influence blogging and Facebook had on interaction, i.e., the number of comments the learners posted outside of class. Student attitudes towards using these tools for written English were also measured through a survey based on the technology acceptance model (Davis, 1989). Twenty-three students at a Japanese university participated in the study and were divided into a Facebook group (n = 14) and a blog group (n = 9) according to their classes. Both groups took part in a ten-week treatment consisting of weekly guided free-writings on their respective Web 2.0 applications. Pre- and post-tests were administered and nonparametric statistical tests were used to determine if any significant writing gains were made. It was found that students in both blogging and Facebook groups showed similar improvements in writing skills. However, blogging seemed to be more effective at promoting interaction and students who took part in this group retained more favorable attitudes on using blogging for L2 writing. It was concluded that Facebook may indeed present an environment where students can be distracted from more formal educational pursuits (e.g. Wang & Kim, 2014) even when they are in private Facebook groups, while blogging may support a more serious environment for improving L2 writing skills.