Abstract Objectives We test whether higher awareness of age-related gains (AARC-gains), lower awareness of age-related losses (AARC-losses), and more positive attitudes toward own aging (ATOA) are cross-sectionally related to more frequent social media use. We also investigate the strength and direction of the associations of AARC-gains, AARC-losses, and ATOA with social media use over 1 year, from before to after the onset of the coronavirus 2019 pandemic. Methods We used cross-sectional data from 8,320 individuals (mean age = 65.95 years; standard deviation = 7.01) and longitudinal data from a subsample of 4,454 individuals participating in the UK PROTECT study in 2019 and 2020. We used ordered regression models, linear regression models, and tests of interaction. Models were adjusted for age, sex, education, and employment. Results Higher AARC-gains and more positive ATOA, but not AARC-losses, were cross-sectionally associated with more frequent social media use. Social media use became more frequent at follow-up. In the longitudinal models controlling for baseline levels of the outcome variable, more frequent baseline social media use predicted increases in AARC-gains, whereas baseline AARC-gains did not significantly predict the frequency of social media use at follow-up. Baseline frequency of social media use did not significantly predict AARC-losses, nor ATOA at follow-up, whereas lower levels of AARC-losses and more positive ATOA predicted more frequent social media use at follow-up. Discussion Although effect sizes were small, decreasing negative views on aging may help increase the engagement of middle-aged and older people with social media. At the same time, fostering social media use could promote positive self-perceptions of aging.