The primary aims of this study are to test the efficacy of a Smartphone-based CBT treatment for adults with SAD recruited nationally. Eligible subjects (N=80) will be randomly assigned to 12 weeks of Smartphone-delivered CBT for SAD either immediately, or after a 12-week long waiting period (50-50 chance). The investigators hypothesize that Smartphone-delivered CBT for SAD will be feasible and acceptable to individuals with SAD, and that it will lead to greater reductions in SAD symptom severity compared to the passage of time (waitlist control).