The adoption of conspiracy theories about COVID-19 has been fairly widespread among the general public and associated with the rejection of self-protective behaviors. Despite their significance, however, a gap remains in our understanding of the underlying characteristics of messages used to disseminate COVID-19 conspiracies. We used the construct of resonance as a framework to examine a sample of more than 1.8 million posts to Twitter about COVID-19 made between April and June 2020. Our analyses focused on the psycholinguistic properties that distinguish conspiracy theory tweets from other COVID-19 topics and predict their spread. COVID-19 conspiracy tweets were distinct and most likely to resonate when they provided explanations and expressed negative emotions. The results highlight the sensemaking functions served by conspiracy tweets in response to the profound upheaval caused by the pandemic.