The purpose of this study is to determine the effects of Facebook and WhatsApp on success in English vocabulary instruction and the learners' opinions about the implementation process. In the study, mixed method model, which combines both quantitative and qualitative data, was used. The success of the students in Facebook, WhatsApp, and control group showed a significant difference between the pretest and posttest, meaning that the learning environments had different effects on the increase of success of students. The analysis revealed that the difference in the mean scores of the students in WhatsApp, Facebook, and control group was significant, and WhatsApp has been more effective in the increase of the success. Although more increase in the mean scores of Facebook group was observed compared with control group, this increase was not found significant. Furthermore, students expressed their willingness to go on the practice not only in their present course, but also in their other courses as well. They also opined positive opinions that learning could also take place unconsciously. However, a few students reacted negatively against the unnecessary messages and the timing of some messages. The results indicated that, compared with Facebook, WhatsApp is more effective in teaching vocabulary.