0001145255 2026-05-28 2026-05-28 0001145255 hnna:CommonStockNoParValueCustomMember 2026-05-28 2026-05-28 0001145255 hnna:NotesDue20264875CustomMember 2026-05-28 2026-05-28 false 0001145255 8-K 2026-05-28 HENNESSY ADVISORS, INC. CA 001-36423 68-0176227 7250 Redwood Blvd. Suite 200 Novato CA 94945 415 899-1555 false false false false Common stock, no par value HNNA NASDAQ 4.875% Notes due 2026 HNNAZ NASDAQ false