Social anxiety disorder (SAD) is the most common anxiety disorder, affecting up to 10% of the population and causing significant distress. Fortunately, there are effective interventions including cognitive behavior therapy (CBT) and acceptance and commitment therapy (ACT). However, only about a third of people with SAD seek treatment. There are a number of barriers to seeking treatment, including cost, availability, and stigma. Self-help may be one way to reach people who may not otherwise present for treatment. Research on self-help books for SAD based on CBT has yielded promising results. However, no research to date has examined the efficacy of ACT-based self-help for SAD. The primary purpose of the present study is to evaluate The Mindfulness and Acceptance-based Workbook for Social Anxiety and Shyness (Fleming & Kocovski, 2013), an ACT-based self-help book. Socially anxious participants will be randomly assigned to receive the workbook or be placed on a waitlist. It is hypothesized that workbook participants will report significantly reduced social anxiety at the end of eight weeks compared to waitlist participants. The secondary purpose is to evaluate how the treatment works. Increases in mindfulness and acceptance have been shown to lead to reduced social anxiety. These same variables will be examined in the present study. Finally, this research aims to examine variables that can predict who may do well in treatment. Given that two-thirds of people who meet criteria for this disorder will not seek traditional treatments, it is important to develop and evaluate alternative treatments, including those based on self-help.