Aim: The coronavirus disease (COVID-19) pandemic has negatively affected access to healthcare and treatment. This study aimed to explore the impact of the COVID-19 pandemic on older adults with out-of-hospital cardiac arrest (OHCA) in Japan, a country with a super-aging society. Methods: This secondary analysis of the All-Japan Utstein Registry included patients aged 65 years and older with bystander-witnessed OHCA between January 1, 2005, and December 31, 2020. Survival outcomes were compared by time period using multivariable logistic regression analyses. The primary outcome measured was the one-month survival rate with neurologically favorable outcomes. Results: Before the COVID-19 pandemic, survival outcomes were steadily improving, and 32,024 patients in 2019 and 31,894 in 2020 were eligible for analysis. The proportions of conventional cardiopulmonary resuscitation and shock by public-access automated external defibrillators were lower in 2020 than in 2019 (6.7% versus 5.7%, p < 0.001 and 2.5% versus 2.1%, p < 0.001, respectively). Compared to 2019, the one-month survival after OHCA and prehospital return of spontaneous circulation decreased significantly in 2020 than in 2019 (7.7% versus 6.6%, adjusted odds ratio [AOR]: 0.88, 95% confidence interval [CI]: 0.83-0.94, and 16.8% versus 14.9%, AOR: 0.87, 95% CI: 0.83-0.91, respectively). The proportion of neurologically favorable outcomes also decreased, but the decrease was not statistically significant (3.4% versus 2.8%, AOR: 0.92, 95% CI: 0.83-1.01). Conclusion: In this population-focused, bystander-witnessed study regarding OHCA, the analysis of nationwide registry data revealed that the COVID-19 pandemic was associated with reduced survival among older adults with OHCA in Japan.