As the COVID-19 pandemic progressed, there was a continued worsening of mental health and well-being of older adults living in England, and socioeconomic inequalities persisted. Greater deterioration in mental health was seen in women and nonpartnered people. Older people did not adapt well to the pandemic-induced new psychosocial stressors.

• This cohort study including 5,146 older adults participating in the English Longitudinal Study of Ageing was conducted to report the impact of COVID-19 pandemic on the mental health and well-being of older adults in England when compared with pre-pandemic levels.

• During June and July 2020, a significant increase in the levels of depression, loneliness, and poor quality of life was evident relative to pre-pandemic levels.

• These kept on deteriorating during the second national lockdown in November and December 2020, with further elevations in anxiety symptoms from June and July 2020 to November and December 2020.

• There were disparities in experiences of mental ill health during the COVID-19 pandemic; especially vulnerable groups were: women, individuals living alone, and those with less wealth.

• Immediate provision of targeted psychological interventions to support older people is required, and access to digital mental health services should be improved.