Previous research has established that happy and sad moods can affect persistence and success on a cognitive task, with happiness leading to higher performance and self-efficacy. Two experiments examined whether happiness also produces increased performance on a physical task and tested whether self-efficacy mediated the results. When mood inductions covered the full range from happy to sad, mood did influence physical performance. However, evidence regarding self-efficacy was equivocal. Efficacy for the performed task was unaffected by mood, although it remained a good predictor of performance. Since mood did alter efficacy for a nonperformed but more familiar task, inconsistent efficacy results could reflect task differences. The findings offer prospects for the use of mood inductions in practical sporting situations.