This study examined age group differences across adulthood in comorbid conditions, mental health, and cognitive function in people with fibromyalgia. Participants completed an online survey about how fibromyalgia affects their everyday life. Chi square analyses were conducted to examine associations between age groups and (a) comorbid conditions and (b) severity of anxiety and depression. ANOVA analyses examined age group differences on aspects of self-report cognitive function. The greatest prevalence of comorbid conditions was found in middle adulthood. Early adulthood was associated with more cases of severe anxiety with the lowest number of cases being in the oldest age group. Middle adulthood was associated with worse self-report pain compared to the youngest age group. Older adults showed better self-report cognitive function compared to younger adults. Distinct age profiles based on comorbid conditions, mental health, and symptom severity across adulthood in fibromyalgia have been demonstrated.