In order to reduce the spread of SARS-CoV-2, much of the US was placed under social distancing guidelines during March 2020 . We characterized risk perceptions and adherence to social distancing recommendations in March 2020 among US adults aged 18+ in an online survey with age and gender quotas to match the general US population (N = 713). We used multivariable logistic and linear regression to estimate associations between age (by generational cohort) and these outcomes . The median perceived risk of infection with COVID-19 within the next month was 32%, and 65% of individuals were practicing more social distancing than before the outbreak . Baby Boomers had lower perceived risk than Millennials (-10.6% , 95% CI: -16.2%, -5.0 %), yet were more frequently social distancing (OR = 1.64; 95% CI : 1.05 , 2.56). Public health outreach should focus on raising compliance with social distancing recommendations, especially among high risk groups . Efforts to address risk perceptions alone may be inadequate.