Background and ObjectivesPre-event rumination has a clear role in maintaining social anxiety according to cognitive models. However, it is unclear what specific strategies can address pre-event rumination for individuals diagnosed with SAD. The current study aimed to determine the effectiveness of a brief intervention on multiple aspects of pre-event rumination, state anxiety and performance and threat appraisals. Additionally, the trajectory of pre-event rumination was investigated over four days. MethodsParticipants with SAD were informed they would be required to complete a speech task in four days' time and were randomised to an intervention (n = 27) or a non-active control group (n = 25). The intervention group were instructed to “ban” pre-event rumination using a metacognitive therapy technique known as detached mindfulness. All participants completed daily measures of pre-evet rumination that assessed frequency, uncontrollability, engagement and distress associated with pre-event rumination. On the day of the speech task, participants also completed state and cognitive measures before delivering the speech task. ResultsThe intervention group reported reduced frequency, uncontrollability and distress associated with pre-event rumination, compared to the control group. There was no difference between groups for performance and threat appraisals as well as state anxiety. Rumination is a stable and robust process, with an increase in frequency and associated distress 24 hours before a feared social situation. LimitationsThe lack of an active control group precludes comparisons to more traditional cognitive-behavioural therapy strategies for pre-event rumination. ConclusionsPre-event rumination is a durable process but banning pre-event rumination using metacognitive therapy techniques shows promise for specifically addressing this maladaptive process.