Like previous pandemics, the coronavirus disease 2019 (COVID-19) has direct and indirect effects, including in mental health. To evaluate the immediate psychological impact of COVID-19, we conducted an online survey in Portugal (24-27 March 2020), using the Impact of Event Scale-Revised (IES-R) and the Depression, Anxiety and Stress Scale (DASS-21). From the 10,529 participants (M = 31.33; SD = 9.73), 83.4% were women, had a mean age of 31.2 years, and 70.9% were active workers. Depression, anxiety, and stress were rated as moderate to severe in 11.7%, 16.9%, and 5.6% of the sample, respectively. Moreover, 49.2% of participants reported a moderate or severe psychological impact of the outbreak. Women, the unemployed, those with lower education, living in rural areas, and with flu-like symptoms or chronic disorders were risk factors. Further research is needed to identify vulnerable groups to better inform and adapt mental health policies and interventions.