Methods and Results: We analyzed the registry data of 2,420 and 2,371 OHCA patients in Osaka City, Japan in 2019 and 2020, respectively, according to the 3 waves of the COVID-19 pandemic. Patient outcomes were compared using multivariable logistic regression analyses with the 2019 data as the reference. Bystander cardiopulmonary resuscitation (CPR) was initiated significantly less frequently in 2020 than in 2019 (2019: 48.0%, 2020: 42.7%, P<0.001), particularly during the first wave (2019: 47.2%, 2020: 42.9%, P=0.046) and second wave (2019: 48.1%, 2020: 41.2%, P=0.010), but not during the third wave (2019: 49.2%, 2020: 44.1%, P=0.066). The public-access automated external defibrillator was less frequently applied during the first wave (2019: 12.6%, 2020: 9.9%, P=0.043), with no significant difference during the second wave (2019: 12.5%, 2020: 12.8%, P=0.863) and third wave (2019: 13.7%, 2020: 13.0%, P=0.722). There was a significant difference in 1-month survival with favorable neurological outcomes (2019: 4.6%, 2020: 3.3%, P=0.018), with a 28% reduction in the adjusted odds ratio in 2020 (0.72; 95% confidence interval: 0.52–0.99, P=0.044).