We investigated changes in alcohol consumption following the COVID-19 lockdown among French-speaking Belgian individuals at risk for severe alcohol use disorder. Participants (N = 299) at risk for alcohol use disorder (AUD, i.e., score higher than 19 at the Alcohol Use Disorder Identification Test), and 299 moderate drinkers (MOD, i.e., score lower than 8) individually matched for age, gender and education provided self-reports of alcohol consumption changes (i.e., number of alcohol units consumed during a typical week before and during lockdown). AUD were more likely (91.31%) than MOD (71.57%) to modify their consumption following lockdown (p < 0.0001). They were more likely to decrease (65.89% vs. 35.12%, p < 0.0001) and less likely to increase (25.42% vs. 36.45%, p = 0.004) their consumption than MOD. Analyses of post-pre lockdown differences in alcohol consumption showed that AUD presented a stronger decrease than MOD (-13.97 units/week vs. -0.07, p < 0.0001). Among individuals who decreased consumption, AUD decreased more (-27.92 vs. -2.74, p < 0.0001) than MOD. Among those who increased consumption, AUD increased more (17.32 vs. 2.44, p < 0.0001) than MOD. We thus observed sharp consumption increases or conversely abrupt decreases in individuals at high risk of alcohol use disorder, underscoring the need to develop prophylactic interventions for this population during such sanitary crises, to avoid brutal changes of the alcohol consumption pattern. Efforts should be made to mitigate consumption increases but also to favor progressive rather than sudden decreases in order to prevent damaging withdrawal symptoms.