Scarce and inconclusive evidence exists on the mental health consequences of the COVID‐19 lockdown. This study examined the psychological impact of the lockdown in Greece, resilience levels, use of coping strategies, and identified high‐risk groups. A sample of 1661 participants (mean age = 39.5, SD = 12.2; 75.5% females) completed a web‐based survey, which was distributed through social networking sites, webpages, and personal contacts. Posttraumatic symptoms, posttraumatic growth, resilience, and coping strategies were assessed. Different population subgroups suffered the impact of lockdown disproportionately. Healthcare workers, females, younger, less educated, and those living alone reported higher rates of posttraumatic stress symptoms. Females achieved more posttraumatic growth and were using coping strategies more frequently than men. Men, older, healthcare workers, and those with a partner were more resilient. Interventions need to be developed to target personal resources, protect vulnerable populations, facilitate posttraumatic growth, and ameliorate wellbeing and quality of life.