Objective: The word repetition technique is used in acceptance and commitment therapy as a method of facilitating cognitive defusion from distressing thoughts. The present study conducted a randomised trial to manipulate the rate of word repetition and evaluate its impact on the efficacy of cognitive defusion. Method: Thirty-two participants repeated a self-chosen negative self-evaluative word for 30 seconds at the rates of one word per 0.5-, 1-, or 2-seconds. Visual analogue scales were used to measure the associated levels of believability and discomfort at pre- and immediately postrepetition, and 1 month later. Results: Both believability and discomfort were significantly reduced immediately after word repetition in the 0.5-seconds and 1-second conditions. There was a significantly greater reduction in Discomfort in the 1-second condition in comparison to the 2-second condition. The 1-second condition alone maintained significant reductions in both believability and discomfort at 1-month follow up. Conclusion: Differences in the cognitive defusion of distressing thoughts appear to be influenced by word repetition rate with repetition rates of one word per 0.5 and 1 seconds somewhat more effective for treating distressing private experiences associated with problem words.