Although it is well documented that attention-deficit/hyperactivity disorder (ADHD) is associated with reduced life satisfaction, the mechanisms that might explain this co-occurrence are unclear. We examined the correlation of ADHD symptoms with life satisfaction and whether this association is mediated by (lacking) social support and depressive symptoms. Self-reported ADHD symptoms, life satisfaction, social support, and depressive symptoms were assessed in a representative, predominantly adult sample from the general population (14–91 years, N = 2517). Attention-deficit/hyperactivity disorder symptoms correlated negatively with life satisfaction (r = −0.41, p < 0.01), even after demographic factors (gender, age, income) and common risk factors (not being in a relationship, being unemployed) were controlled for (r = −0.39, p < 0.01). Social support mediated up to 23% and depressive symptoms up to 44% in the association between ADHD symptoms and life satisfaction. Counteracting problems with social relationships and treating depressive symptoms may help to increase life satisfaction in adults with ADHD symptoms.