The aim of the study was to test the effectiveness of a serious game in improving the helping behaviours of bystanders in bullying situations by using a multimethod approach. Students (N=345, aged 12 to 14) participated in an experimental study with one experimental and two control groups. Before and after playing the game, all students completed an online questionnaire about their knowledge, experiences and behaviours related to bullying, and their behaviours in everyday social situations. For the experimental group, players' reactions during game-play were recorded. Results showed that students' social behaviour displayed before gaming experience determined their playing activities. Besides, most of the students who declared in pre-test that they do not help the victim, although they think they should, chose helping behaviour in all bullying situations in bystander role in the game. Results indicate weak positive effect of the game on students' behavioural choices.