Blended learning is a combination of traditional and technology-enhanced learning. Social networks services can be used in blended learning settings as they support collaboration, resource sharing, and socialization. Edmodo is an educational social network which can facilitate the development of second or foreign language skills. This study intended to investigate the effects of blended learning through implementing Edmodo mobile application on the academic writing proficiency and perceptions of Iranian intermediate EFL learners in higher education. This quasi-experimental research followed a mixed method design. The results indicated that it was possible to integrate Edmodo mobile application into essay writing class successfully since the experimental group who practiced collaborative essay writing through Edmodo mobile application outperformed the control group regarding writing proficiency in general as well as such aspects as organization, vocabulary, and mechanics of writing. The qualitative analysis of follow-up interviews revealed that majority of students had positive opinions and perceived it as an innovative, engaging and helpful activity. Blended Language Learning is a promising area in the field of TEFL, and as such it is crucial for teachers to keep their teaching methodologies and techniques compliant with the technology developments of 21st century.