This study intends to examine English as a foreign language (EFL) learners' attitudes toward practicing English in Second Life (SL) and to unpack the effects of avatar identities on EFL learners' sense of self-efficacy and language practices. Nine EFL learners worldwide participated in a task-based course in SL, using avatars to carry out SL-related tasks while interacting with peers and the teacher via voice chat. Qualitative data were triangulated from multiple sources: learner reflective journals, a post-course survey, and semi-structured interviews. Three major themes emerged: (1) the effects of masked identity on learning; (2) the impact of telepresence and copresence on learning; and (3) the perceived attitudes toward avatar affinity. Findings implicate that the avatar form renders masked identities to safeguard learners' self-efficacy and empower their language practices. It also opens up a research avenue on the impact of avatar identities on language learning and teaching in 3D virtual environments.