Contemplative approaches rooted in Buddhist traditions have been linked to the attenuation of response to social stress. Anticipatory cognitive appraisals of social situations potentially represent a mechanism explaining the stress-reducing effects of contemplative practices. The cognitive appraisal of threat is associated with an anticipated loss of social self-esteem. In contrast, the cognitive appraisal of challenge involves recognizing the potential for gain or growth in stressful situations and is associated with a more adaptive cardiovascular response. In this secondary analysis of a randomized controlled experiment performed in Switzerland, we evaluated the effects of two contemplative interventions on cognitive appraisals of challenge and threat and associated physiological profiles. The interventions were a standard Mindfulness-Based Stress Reduction (MBSR) program and a new program (MBSR-B), which included several elements from Buddhist practices. After an eight-week intervention, participants completed the Trier Social Stress Test (TSST) and underwent the assessment of primary cognitive appraisals and cardiovascular response to stress. The results demonstrated greater challenge appraisal in the MBSR (n = 20) and MBSR-B (n = 21) groups compared to Control (n = 24), and MBSR-B participants scored higher on the challenge than threat appraisal. At the physiological level, the groups did not differ on changes in cardiac output and total peripheral resistance. Still, an exploratory analysis demonstrated that the MBSR-B group's cardiovascular profile best resembled challenge appraisal. The results suggest that contemplative approaches foster challenge appraisal, contributing to a more adaptive response to stress.