Social anxiety disorder (SAD) is highly prevalent and associated with a substantial societal economic burden, primarily due to high costs of productivity loss. Cognitive behavior group therapy (CBGT) is an effective treatment for SAD and the most established in clinical practice. Internet-based cognitive behavior therapy (ICBT) has demonstrated efficacy in several trials in recent years. No study has however investigated the cost-effectiveness of ICBT compared to CBGT from a societal perspective, i.e. an analysis where both direct and indirect costs are included. The aim of the present study was to investigate the cost-effectiveness of ICBT compared to CBGT from a societal perspective using a prospective design. We conducted a randomized controlled trial where participants with SAD were randomized to ICBT (n=64) or CBGT (n=62). Economic data were assessed at pre-treatment, immediately following treatment and six months after treatment. Results showed that the gross total costs were significantly reduced at six-month follow-up, compared to pre-treatment in both treatment conditions. As both treatments were equivalent in reducing social anxiety and gross total costs, ICBT was more cost-effective due to lower intervention costs. We conclude that ICBT can be more cost-effective than CBGT in the treatment of SAD and that both treatments reduce societal costs for SAD.