Objectives: A 6-week multicomponent positive psychology intervention (PPI) was assessed with the primary aim of determining its effects on affective variables including anxiety, depression and psychological distress, as well as processual ones, such as mindfulness and emotion regulation. Exploratory investigations were conducted to consider changes in individual differences according to baseline characteristics. Method: Participants were from a community sample of the French population. They were assigned to the control (n = 43) or intervention group (n = 59). Self-assessment measures included the Mindful Attention Awareness Scale, Cognitive Emotion Regulation Questionnaire, Spielberger State-Trait Anxiety Inventory, Beck Depression Inventory and the General Health Questionnaire. Results: Trait anxiety, depressive symptoms and psychological distress significantly decreased over the course of the PPI in comparison to the control group. Regarding processual variables, mindfulness increased with a large effect size, acceptance and positive reappraisal increased, and scores for otherblame strategy significantly decreased. Exploratory analyses showed that mindfulness and positive reappraisal tended to increase even more when participants' initial levels were low. Conclusion: Future clinical interventions should account for baseline characteristics to ensure that participants are referred to the most effective, suitable programs for their own needs.