Background: Older individuals are at increased risk of a severe and lethal course of COVID-19, the respiratory disease caused by the new coronavirus SARS-CoV-2. During lockdowns to curb the spread of the virus, older individuals have typically been advised to practice particularly restrictive social distancing, often referred to as ‘cocooning’. Whether the COVID-19 vulnerability and cocooning impact the mental and social health of older individuals has sparked much debate. We aim to provide data-based evidence. Methods: Computer-assisted standardized telephone interviews were conducted in a randomly selected, representative sample of the German old age population (n = 1,005; age ≥ 65 years) during lockdown in April 2020. Assessments included sociodemographic factors, aspects of the personal life situation during lockdown, attitudes towards COVID-19, and standardized screening instruments for depression, anxiety, somatization, posttraumatic stress, perceived stress, loneliness and social support as well as indicators of social isolation. Sampling-weighted descriptive statistics and multiple multivariable regression analyses were conducted. Results: Participants were M = 75.5 (SD = 7.1, range = 65-94) years old; 56.3% were women. At time of data collection, COVID-19 lockdown had been in force for M = 28.0 (SD = 4.8) days. Overall, older individuals were worried about COVID-19, but understanding and supportive of the COVID-19 lockdown. Mean scores and prevalences of measured mental and social health variables were comparable to figures reported before the pandemic, except slightly higher perceived stress und higher perceived social support. There were only few significant associations of aspects of the personal life situation during lockdown and attitudes towards COVID-19 with mental and social health variables, with resilience explaining a large amount of variance. Conclusions: In the short-term, the mental and social health of the German old age population was largely unaltered during COVID-19 lockdown, suggesting resilience against the challenging pandemic situation. Our results refute common ageist stereotypes of “the weak and vulnerable elderly” that were present during the pandemic. Long-term observations over the course of the pandemic and post-pandemic are needed to provide robust evidence.