Background: Research suggested that preexisting mental disorders, particularly generalized anxiety disorder (GAD), might increase the already elevated risk of responding to the COVID-19 pandemic with mental health impairments. The present follow-up study investigated the course of GAD symptoms during the pandemic in former outpatients (N = 86) of two randomized controlled trials who were treated with cognitive behavioral therapy (CBT) up to eight years ago. Methods: GAD symptomatology was examined as the probability for a “well month”, that is, a month with no or minimal symptoms, as assessed by the Longitudinal Interval Follow-Up Evaluation (LIFE), taking the periods pre-pandemic, early pandemic, lockdown, and post-lockdown into account, and considering depressive symptoms post-treatment as its predictor. Results: Generalized linear mixed models revealed lower odds ratios for a “well month” during the early pandemic period and higher odds ratios post-lockdown compared with pre-pandemic. Post-treatment depressive symptoms proved to be a significant predictor since pandemic onset. Strategies learned in CBT were analyzed for their applicability and helpfulness in coping with worries during the pandemic. Six particularly helpful strategies were identified by participants. Limitations: Although attrition was comparably low with no indication of an association between missingness and primary outcomes, bias cannot be ruled out. Conclusions: The findings provide preliminary support for the resilience of former CBT patients with GAD during COVID-19, for the long-term relevance of CBT strategies, and for post-treatment depressive symptoms as risk factors for exacerbation of GAD symptoms since the onset of the COVID-19 pandemic.