Role-playing games (RPGs) are considered a useful way of addressing socioscientific issues (SSIs) in the science classroom insofar as they allow learners to engage with an issue and possibly change their opinions on it. This study analyses changes in preservice primary teachers (PPTs) personal positions on nuclear energy following participation in an RPG that simulated a televised debate about the proposal to close nuclear power plants in Spain. The 78 PPTs had to state their position on this issue both before and after the RPG, choosing from among the following three options:(1) immediate closure of nuclear plants, (2) gradual phasing out of nuclear plants or (3) continuing indefinitely with nuclear plants. The majority of students were initially against the future use of nuclear energy, but almost half changed their position following the RPG. Students' initial personal position and the extent to which this disagreed with the position they had to defend in role were factors related to opinion change, both in terms of its direction (towards a position more in favour of or more against nuclear power) and its magnitude (abrupt: from one extreme position to the other; or moderate: from the intermediate to an extreme position, or vice-versa). The analysis also showed that students' personal position after the RPG tended to be closer to that of the role they had portrayed. These aspects should be borne in mind when designing RPGs to address SSIs in the science classroom.