Previous research has considered the effects of content familiarity and task repetition on second language (L2) performance, but few studies have looked at the effect of these factors on learners' engagement in task performance. This study explores the influence of content familiarity and task repetition on English as a foreign language (EFL) learners' engagement in oral performance. Sixty EFL learners performed four narrative tasks with two familiar and two unfamiliar topics. They also repeated the same tasks to the same audience. Their oral production was analysed with various measures of behavioural and cognitive engagement. Stimulated recalls were collected from twenty-one participants to capture their emotional engagement. The participants were behaviourally and cognitively more engaged in tasks with familiar topics as well as having a more positive affective response to them. Repeating the tasks, however, negatively influenced behavioural and cognitive engagement, although the participants felt more relaxed and confident. In addition, the participants were more motivated to repeat unfamiliar topics, although they demonstrated more noticeable declines in their frequency of self-repair (an indicator of cognitive engagement) for these topics. These results provided empirical evidence for the relationship between task design and implementation factors and L2 task engagement. Teachers might base repetition decisions partially on learners' familiarity with the topic.