Cognitive behavioral group therapy (CBGT) has been reported to be more effective than a mindfulness-based stress reduction program (MBSR) in reducing symptoms of social anxiety disorder (SAD). The present study determined whether CBGT and MBSR differentially affected subjective anxiety and physiological response to a stressful speaking task. The sample comprised 38 medication-free SAD patients who participated in a previously published trial comparing CBGT and MBSR; an additional 30 participants were healthy control (HC) volunteers. Patients performed a speech task before and after treatment while HC performed it only once. Subjective anxiety and core symptoms of SAD were assessed with visual analog scales (VAS), and physiological responses included salivary cortisol and heart rate variability. Prior to treatment, the speech task induced greater increases in anxiety and SAD symptoms in patients compared to HC. After treatment, VAS ratings during the task decreased in both treatment groups. The most significant improvement overall was observed with CBGT, with their responses being comparable to that of HC. No physiological differences were found as a function of treatment. Although CBGT produced the best results, MBSR was nonetheless associated with a significant decrease in subjective anxiety and symptoms of SAD during the speech task.