Social networking for language learning (SNLL) entails students practicing second language (L2) writing on social media platforms like Facebook. Language learning through social media activities occurs through active participation resulting in language output. This examination of how L2 output influences language learning highlights the importance of interactions when participating on social network sites. Self-efficacy refers to confidence to succeed and task value refers to the value SNLL has towards helping students meet their language learning goals. Self-efficacy and task value in the context of SNLL are two motivational factors that influence participation and, consequently, language acquisition. This quantitative study surveyed a group of students (n = 203) who participated in a six-week SNLL program in South Korea to investigate the relationships among task value, self-efficacy, and participation. Furthermore, a mediation model was carried out. Results showed that self-efficacy completely mediates the relationship between task value and participation, indicating that increasing levels of self-efficacy explain the relationship between the value SNLL contributes to language learning goals and participation in EFL class Facebook groups. Results-driven pedagogical implications on SNLL are given.