The COVID-19 pandemic caused the largest disruption to graduate medical education in modern history. The danger associated with SARS-CoV-2 necessitated a paradigm shift regarding the fundamental approach to the education of medical residents and fellows. Whereas prior work has examined the effect of the pandemic on residents' experiences during training, the effect of the pandemic on academic performance of critical care medicine (CCM) fellows is not well understood. This study examined the relationship between CCM fellow's lived experiences during the COVID-19 pandemic and performance on in-training examinations. This mixed-methods study consisted of a quantitative retrospective analysis of critical care fellows' in-training examination scores and a qualitative, interview-based phenomenological examination of fellows' experiences during the pandemic while training in a single large academic hospital in the American Midwest. Quantitative: Prepandemic (2019 and 2020) and intrapandemic (2021 and 2022) in-training examination scores were analyzed utilizing an independent samples t test to determine whether a significant change occurred during the pandemic. Qualitative: Individual semi-structured interviews were conducted with CCM fellows exploring their lived experiences during the pandemic and their perception of the effect on their academic performance. Transcribed interviews were analyzed for thematic patterns. These themes were coded and categorized, and subcategories were developed as indicated during the analysis. The identified codes were then analyzed for thematic connections and apparent patterns. Relationships between themes and categories were analyzed. This process was continued until a coherent picture could be assembled from the data to answer the research questions. Analysis was performed from a phenomenological perspective with an emphasis on interpretation of the data from the participants' perspectives. Quantitative: Fifty-one in-training examination scores from 2019 to 2022 were obtained for analysis. Scores from 2019 to 2020 were grouped as prepandemic scores, while scores from 2021 to 2022 were grouped as intrapandemic scores. Twenty-four prepandemic and 27 intrapandemic scores were included in the final analysis. A significant difference was found between mean total prepandemic and intrapandemic in-service examination scores (t 49=2.64, p=0.01), with mean intrapandemic scores being 4.5 points lower than prepandemic scores (95 % CI, 1.08-7.92). Qualitative: Interviews were conducted with eight CCM fellows. Thematic analysis of the qualitative interviews revealed three main themes: psychosocial/emotional effects, effects on training, and effects on health. The factors that most effected participants' perceptions of their training were burnout, isolation, increased workload, decreased bedside teaching, decreased formal academic training opportunities, decreased procedural experience, a lack of an external reference point for normal training in CCM, fear of spreading COVID-19, and neglect of personal health during the pandemic. In-training examination scores decreased significantly during the COVID-19 pandemic for CCM fellows in this study. The fellows in this study reported perceived effects of the pandemic on their psychosocial/emotional well-being, medical training, and health.