Social media platforms are known to foster extremist rhetoric and ideologies, including antisemitism. Antisemitic conspiracy theories are often spread via mainstream social media platforms, including Twitter, especially during times of civic unrest. The COVID-19 pandemic has created an opportunity for the alignment of long-standing antisemitic conspiracies with an international health crisis. This paper applies a mixed-methods approach of data analysis and qualitative coding to examine connections between COVID-19 conspiracy theories and antisemitism in tweets in the U.S. We identify six prominent categories of COVID-19 conspiracy present on Twitter, each of which overlaps with common themes seen in antisemitic conspiracies. This conspiratorial content may be less likely to violate social media hate speech policies but nonetheless contributes to extremist discourse. [Note: this is a full paper to accompany the presentation at the International Communication Associations (ICA) Conference 2023.]