Socially anxious individuals exhibit cognitive performance impairments; it is unclear whether this is due to trait differences in abilities or effects of the experimental context. This study sought to determine how social context, individual differences in fear of negative evaluation (FNE), and task difficulty interact to influence working memory performance as indicated by effectiveness (accuracy) and efficiency (reaction times). Participants (N = 61) performed the n-back task at 2-back and 3-back difficulty levels under three conditions: alone (“Anonymous”), in presence of a non-evaluative experimenter (“Presence”), and under explicit performance evaluation by the experimenter (“Threat”). Overall, participants showed improved accuracy during Threat, but only on 2-back trials. FNE was positively associated with longer reaction times during Threat on 3-back trials. FNE did not relate to accuracy, suggesting that threat-related impairments tied to social anxiety may alter efficiency rather than effectiveness. Thus, social anxiety may elicit cognitive performance impairments even in minimally evaluative environments.