Studies have identified formal volunteer activity as having mental health benefits. This study set out to investigate the role of formal volunteering in the context of psychological flourishing in Scandinavia. Using the European Social Survey conducted in 2006 and 2012, nationally representative cross-sectional data from 7,078 to 7,318 participants aged 15 years and older in Scandinavia were analyzed to assess associations between volunteering and flourishing. The adjusted models for 2006/2012 showed that compared with nonvolunteering, volunteering once per week was associated with twice the likelihood of flourishing—2006: odds ratios (OR) = 2.04 (95 percent confidence interval [CI] = [1.15, 3.62]); 2012: OR = 2.05 (95 percent CI = [1.30, 3.24]). This appeared to be the case across pre- and postretirement age. Volunteering is an activity that not only benefits society but is also associated with optimal mental health in the general population.