In this article, we propose and test within-person hypotheses about real-time correlates of momentary performance and emotions while working. Experience sampling methodology was used to prompt repeated reports of momentary task cognitions and emotions. Hypotheses were largely supported, with task difficulty, skill, interest, and effort predicting momentary perceived performance within person. Task interest had an effect on performance beyond that due to its contribution to effort. Skill, interest, effort, and performance predicted concurrent emotions. The effect of effort on positive emotions was fully mediated through performance, whereas interest had an effect on emotions beyond performance. The effects of skill and effort on emotions changed sign when performance was controlled, suggesting that it is unpleasant to be skilled or exert effort when performance does not improve commensurately. Perceived performance accounts for unique variance in emotions beyond that due to other predictors. Further within-person research on real-time motivation, performance, and emotions is encouraged.