The online proliferation of COVID-19 misinformation led to adverse health and societal consequences. This study investigated possible differences in COVID-19 headline accuracy discernment and online sharing of COVID-19 misinformation between older and younger adults, as well as the role of individual differences in global cognition, health literacy and verbal IQ. Fifty-two younger (18-35 years old) and fifty older adults (age 50 and older) completed a neurocognitive battery, health literacy and numeracy measures, and self-report questionnaires via telephone. Participants also completed a social media headline-sharing experiment (Pennycook et al., Psychological science, 31(7), 770-780, 2020) in which they were presented with true and false COVID-19 headlines about which they indicated: 1) the likelihood that they would share the story on social media; and 2) the factual accuracy of the story. A repeated measures multivariate analysis of variance controlling for gender and race/ethnicity showed no effects of age (p = .099) but a significant interaction between actual COVID-19 headline accuracy and the likelihood of sharing (p < .001), such that accuracy was more strongly related to sharing false headlines (r = −.64) versus true headlines (r = −.43). Moreover, a higher likelihood of sharing false COVID-19 headlines was associated with lower verbal IQ and numeracy skills in older adults (rs = −.51--.40) and with lower verbal IQ, numeracy, and global cognition in younger adults (rs = −.66--.60). Findings indicate that headline accuracy judgements, numeracy, and verbal IQ are important contributors to sharing COVID-19 misinformation in both older and younger adults. Future work might examine the benefits of psychoeducation for improving health and science literacy for COVID-19.