The workload of many residents and fellows in otolaryngology-head and neck surgery has particularly increased during the COVID-19 pandemic; however, outcomes associated with mental health status and sleep remain unclear. To assess the sleep, mental status, and alcohol and tobacco consumption habits of residents and fellows before the COVID-19 pandemic (before March 10, 2020) and during the pandemic period (after March 10, 2020). This cohort study included residents and fellows of 6 university hospitals of European regions with a high prevalence of COVID-19 cases. Survey development, data collection, and analyses were performed from March 10, 2020, to June 30, 2021. Residents and fellows were invited to respond to a survey assessing management of treatment in patients with COVID-19 and related work features; stress and mental health status (Beck Depression Inventory); sleep features (Insomnia Severity Index); and alcohol and tobacco consumption. Of 220 potential participants, 128 residents and fellows (58.2%) completed the evaluations. No demographic data on mean (SD) age and sex or gender were collected. The prepandemic mean (SD) score of the Beck Depression Inventory (3.1 [2.8]) significantly increased after the start of the pandemic (mean [SD] score, 4.2 [4.1]; difference, -1.1; 95% CI, -1.96 to -0.24; d = 0.31), and the prepandemic mean (SD) score of the Insomnia Severity Index (4.9 [4.1) significantly increased after the start of the pandemic (mean [SD] score, 6.0 [4.9]; difference, 1.1; 95% CI, 0.00-2.2; d = 0.25). Insomnia concerned 46% of participants (51 of 112), and depression concerned 47% of participants (55 of 116) during the pandemic. The mean (SD) prepandemic alcohol consumption (1.7 [2.3] IU per week) significantly increased after the start of the pandemic (mean [SD], 2.9 [4.0] IU per week; difference, 1.2; 95% CI, 0.40-2.00; d = 0.37). Residents and fellows who were mobilized in COVID-19 units reported significant increases of workload (r = 0.2; 95% CI, 0.1-0.3), stress level (r = 0.2; 95% CI, 0.1-0.3), and alcohol consumption (for 5-10 IU per week: mean [SD] prepandemic, 11 [8] IU per week vs postpandemic, 20 [16] IU per week; d = 0.37) and a worsening of sleep status (for moderate insomnia: mean [SD] prepandemic Insomnia Severity Index, 4 [3] vs postpandemic, 15 [12]; d = 0.25). There was a significant association between alcohol consumption and the Beck Depression Inventory score (r = 0.4; 95% CI, 0.2-0.6). The mean (SD) consumption of tobacco decreased from 2.1 (1.3) to 0.9 (1.5) (difference, -1.20; 95% CI, -1.50 to -0.85; d = 0.85). Results of this cohort study suggest that the workload of residents and fellows increased during the pandemic, which may be associated with a worsening of mental health and sleep status and an increase of alcohol consumption.