Greece imposed a nationwide lockdown in March 2020 to mitigate transmission of severe acute respiratory syndrome coronavirus 2 during the first epidemic wave. We conducted a survey on age-specific social contact patterns to assess effects of physical distancing measures and used a susceptible-exposed-infectious-recovered model to simulate the epidemic. Because multiple distancing measures were implemented simultaneously, we assessed their overall effects and the contribution of each measure. Before measures were implemented, the estimated basic reproduction number (R ) was 2.38 (95% CI 2.01-2.80). During lockdown, daily contacts decreased by 86.9% and R decreased by 81.0% (95% credible interval CrI 71.8%-86.0%); each distancing measure decreased R by 10%-24%. By April 26, the attack rate in Greece was 0.12% (95% CrI 0.06%-0.26%), one of the lowest in Europe, and the infection fatality ratio was 1.12% (95% CrI 0.55%-2.31%). Multiple social distancing measures contained the first epidemic wave in Greece.