The role that the involvement of parents may play in the treatment outcome of their children with anxiety disorders is still under debate. Some studies dealing with other disorders have examined the role that the expressed emotion (EE) construct (parental overinvolvement, criticism and hostility) may play in treatment outcome and relapse. Given that some of these aspects have been associated with social anxiety for a long time, it was hypothesized that EE may be associated with lower treatment outcome. The sample was composed of 16 adolescents who benefited from a school-based, cognitive-behavioural intervention aimed at overcoming social anxiety. Then, parents were classified with high or low EE. The results revealed that the adolescents whose parents had low EE showed a statistically significant reduction of their social anxiety scores at posttest, as opposed to adolescents of parents with high expressed emotion. These findings suggest that parental psychopathology (parents with high EE) should be taken into consideration to prevent poor adolescent treatment outcome.