Performance-avoidance goals (the desire to avoid performing more poorly than others do) have been shown to have consistently deleterious effects on performance but the effects of performance-approach goals (trying to outperform others) are more complex. Two studies examine uncertainty as a moderator of the effect of performance-approach goals on performance. Experiment 1 shows that manipulated performance-approach goals lead to better performance than do performance-avoidance goals in the absence of uncertainty about performance but when participants learn that a coactor disagreed with them about problem solutions, creating uncertainty, performance-approach goals do not differ from performance-avoidance goals in their effect on performance. Experiment 2 shows that uncertainty also moderates the effects of self-set performance-approach goals. Moreover, the same dynamic occurs with another kind of uncertainty: negative competence feedback.