The negative affective priming (NAP) task is a behavioral measure of inhibition of emotional stimuli. Previous studies using the NAP task have found that individuals with depression show reduced inhibition of negative stimuli, suggesting that inhibition biases may play a role in the etiology and maintenance of depression. However, the psychometric properties of the NAP task have not been evaluated or reported. In the present study, we report data on the association between NAP task performance and depression symptoms in three independent samples, and we evaluate the internal consistency and test–retest reliability of the NAP effect indices. The NAP effect for both negative and positive target words had poor internal consistency in all three samples, as well as poor 2-week (Study 2) and 6-month (Study 3) test–retest reliability. The internal consistency and test–retest reliability of response times (RT) for the individual trial types were moderate to high, as were the intercorrelations between trial types. This pattern of results indicates that overall RT is reliable but variance in RTs for the different trial types in the NAP task is indistinguishable from variance in overall RT. Depression symptom severity was not associated with the NAP effect for negative or positive target words in any of the samples, which could be due to the poor reliability of the NAP effect. Based on these findings, we do not recommend that researchers use the NAP task as a measure of individual differences in the inhibition of emotional stimuli.