Juries in many Western countries are being asked to make decisions about defendants charged with terrorist-related offences, in situations where heightened anxieties and hostility to outgroups may make a fair trial difficult. What impact can deliberation have in addressing any such prejudice? This study estimates the impact of several forms of prejudice on juror verdicts in a mock terrorism trial. The study provides a more realistic setting than most previous studies, with an authentic heritage courtroom, actual jury assembly room and jury deliberation rooms in the NSW Supreme Court, a one-hour live trial and one-hour deliberation. Strong relationships are found between conviction rates and prior attitudes before jury discussion, consistent with other literature. Deliberation significantly reduces the proportion of guilty verdicts; it also reduces the impact on verdict of two forms of prejudice – fear of terrorism and punitiveness. On the other hand it tends to increase the impact of cognitive prejudice, measured both by a modified version of the Jury Bias Scale and a terrorism-specific scale based on attitudes to Australian Guantanamo Bay detainee David Hicks.