This paper reports on an experimental research study that aimed at investigating the effectiveness of employing a virtual task-based situated language learning (TBSLL) environment mediated by Second Life (SL) in developing EFL student teachers' pragmatic writing skills and their technological self-efficacy. To reach this goal, a control-only experimental research design was employed to compare between participants' performance in two groups: a control group (n = 10) exposed to a traditional lecture-based writing course; and an experimental (SL) group selected purposively (n = 10) and exposed to the virtual SL situated language learning environment (online sessions). Procedures were guided by a "five-stage instructional-technological design framework" suggested by the researchers, which involved those stages: (1) analysis, (2) design, (3) production, (4) experimentation, and (5) use & development. Measurement tools included: (a) Pragmatic Writing Skills Post-Test; (b) Academic Self-Efficacy Scale; and (c) E-portfolio for formative assessment. Results indicated the effectiveness of the virtual task-based situated language environment in developing participants' pragmatic writing skills in English, and that SL participants' technological self-efficacy was significantly higher than that of the control group participants. The paper presents recommendations and suggestions for improving English language learning (ELL)--especially writing--through using virtual situated environments in general, and SL in particular. The following are appended: (1) Pragmatic Writing Test (Examiner's Manual and Students' Version); (2) Technological Self-Efficacy Scale; and (3) E-Portfolio: A Reflective Diary Template.