People often overestimate the intensity and duration of their future emotions, referred to as an impact bias. Impact biases have been documented in predictions people make about their own emotions, as well as the others' emotions (i.e., affective and empathic forecasting, respectively). Recent studies have shown that negative impact biases may be stronger, and positive impact biases may be attenuated, in individuals with symptoms of social anxiety. The current study sought to replicate and extend these findings in a Mechanical Turk (MTurk) sample. MTurk is a particularly interesting online platform for such research because of the unusually high prevalence of social anxiety among MTurk users. Within a computer-based survey, 93 MTurk users read vignettes in which a second-person narrator elicited either disgust, anger, or happiness from another person. After each vignette, participants predicted how the narrator (i.e., affective forecasts) and the other person (i.e., empathic forecasts) would feel. Overall, results confirmed the existence of associations between social anxiety symptoms and negative affective and empathic forecasting biases, though no significant relations were found between social anxiety symptoms and positive forecasting biases. Negative affective and empathic forecasting biases were significantly correlated. Age and gender were also examined as potential predictors and moderators of hypothesized effects. Though younger age and female gender were associated with specific forecast ratings, controlling for these variables did not alter the associations between social anxiety and affective or empathic forecasts and no moderation effects were found. Overall, results provide additional support for the relevance of impact biases to social anxiety and suggest that they may be useful targets of intervention.