ABSTRACT Science and religion are important topics that people have opportunities to discuss in both online and offline contexts. Why do people prefer one communication mode over the other? Analyzing interviews with 45 adults from across the United States, we look at why people prefer communicating online versus offline about science and religion. Findings show that characteristics unique to either mode of communication (asynchronous communication, detachment, visual and social cues) are key factors in shaping people's preferences. We highlight principal differences in how these factors appear across science and religion. We also find that some people's preference toward online or offline communication depends on the context, such as the focus of the discussion or the relationship with the interlocutor. Understanding people's reasons for choosing to communicate about science and religion online versus offline can support related communities in creating more effective discussion options in the future.