Objectives-We investigated (1) age of onset of hoarding disorder (HD) symptoms and diagnosis, (2) late-onset HD, (3) progression of HD symptoms, and (4) association between demographics and hoarding progression.Method-Eighty-two older adults with HD provided retrospective ratings of their hoarding symptoms for each decade of life. Age of onset of symptoms (saving, difficulty discarding, and clutter) was operationalized as the first decade in which the participant reported at least minor symptom severity, and age of onset for possible HD diagnosis was operationalized as the first decade in which the participant reported all three symptoms. We used mixed effects modeling to examine the progression of HD symptoms.Results-The median age of onset for symptoms was between 10 and 20 years, and the median age of onset for possible HD diagnosis was between 20 and 30 years. Twenty-three percent of participants reported onset of possible HD diagnosis after the age of 40. All HD symptoms increased in severity over time. Men reported higher initial clutter and a slower increase in hoarding severity for all symptoms. Increased education was associated with slower increase in saving. Having at least one parent with hoarding tendencies was associated with higher initial hoarding symptoms.Conclusion-Generally, symptoms of HD begin relatively early and worsen across the lifespan. However, approximately one fourth of older adults with HD reported a possible onset after the age of 40.