Previous research indicates that the reward positivity (RewP), an electrophysiological correlate of sensitivity and biases towards rewarding stimuli, is modulated by affective and motivational variables. Studies have provided evidence that states and traits associated with negative affect and reduced approach motivation are correlated with smaller RewP amplitudes. However, the possible confound of affective valence and motivational direction was not addressed in these studies. In the present study, we examined if anger, an emotion associated with negative affect and increased approach motivation, would affect RewP amplitude. We also investigated if RewP amplitude was related to the motivational properties of reward stimuli. One hundred male participants completed two emotion inductions intended to elicit feelings of either neutrality or anger. Each was followed by a simple gambling task, in which correct choices were followed by images of women in lingerie or swimwear. Although the RewP was elicited following each induction, there was no difference in amplitude between the neutral and anger induction. However, RewP amplitude was positively correlated with how much participants liked the reward stimuli, and this correlation was statistically larger following the anger induction. These results support a motivational interpretation for the differences in RewP amplitude reported in previous studies, suggesting that motivational direction and intensity, rather than affective valence, underlie differences in RewP amplitude. Moreover, the RewP appears to be affected by interactions between motivational state and the motivational value of reward stimuli.