We tested a hypothetical model that examined both the effects of implicit theories of ability on the judgement of cheating acceptability in a physical education context and the mediating role of the achievement goals defined in the social-cognitive model of achievement motivation. Data were collected from 477 middle-school students, who completed measures of implicit theories of ability, achievement goals, and judgement of cheating acceptability in team sports within a cross-sectional design. The results indicated that performance-approach and performance-avoidance goals mediated the relationships between entity theory and the judgement of cheating acceptability, and mastery-approach and mastery-avoidance goals mediated the relationships between incremental theory and the judgement of cheating acceptability. Further research is needed to determine whether these results would be replicated with other moral variables and other contexts.