Aim: Social engagement is known to serve an important role in cognitive health, but there has been limited information on the role of online engagement. The present study aimed to identify the benefits of different online activities for the cognitive function of older adults.Methods: Data came from the National Health and Aging Trend Study, Round I-V (2011)(2012)(2013)(2014)(2015), with >8000 respondents from Medicare beneficiaries. Cognitive function was measured by the Clock Drawing Test and immediate 10-word recall. The respondents were also asked if they carried out any of the online activities listed.Results: Some online activities, such as email, texting and seeking medical information, can reduce the risk of cognitive decline. Whereas contacting a medical provider using online can increase the risk of cognitive decline.Conclusions: Given the findings, the development of new technologies for online social engagement needs to be one of the priorities for researchers and policymakers in the field of aging and dementia. Geriatr Gerontol Int 2019; 19: 918-923.the USA. The secondary sample units were selected based on the ZIP codes, and respondents in each ZIP code were selected upon considering the proportion of the race/ethnicity (non-Hispanic Black, Hispanic, White and other) and age in the population of the same ZIP code. 14 ‡ Native American, Asian, Native Hawaiian, Pacific Islander, other non-Hispanic.