INTRODUCTION: The COVID-19 pandemic has presented population-wide novel stressors. Acceptance and Commitment Therapy (ACT) may be potent for coping with novel, unpredictable stressors, but it is unknown whether pre-pandemic ACT treatment conferred protective benefit during the COVID-19 pandemic. METHODS: Participants (N = 73) from a previous randomized controlled trial of ACT (seven 2-hour group sessions) versus minimally-enhanced usual care (MEUC) for anxious cancer survivors completed measures of anxiety symptoms, fear of cancer recurrence, and emotional approach coping during the trial and again during the pandemic in May, June/July, and November 2020, an average of 2.71 years after completing ACT or MEUC. We estimated hierarchical linear models to test overall and conditional differences over the trial timepoints, in the interval between the trial and May 2020, and between the pandemic timepoints. RESULTS: Compared to MEUC, ACT led to greater improvement on the outcomes during the 8 month trial follow-up, consistent with the main trial findings. Across the entire sample, anxiety symptoms and emotional approach coping worsened from the final trial assessment timepoint to May 2020 (ps < .001). During this period, ACT participants worsened significantly more on emotional approach coping (p = .035) than MEUC participants. No significant condition differences emerged at later pandemic timepoints.CONCLUSIONS: Treatment with ACT several years earlier did not provide protective benefit to anxious cancer survivors during the pandemic, relative to MEUC. ACT interventions may need to be targeted to pandemic-specific stressors, or booster sessions may be required for prior ACT treatment completers when faced with novel stressors.