Systemic reactive amyloid A (AA) amyloidosis is one of the critical complications associated with rheumatoid arthritis (RA). Recently, there are several useful reports of anti-tumor necrosis factor therapy for RA-related systemic reactive AA amyloidosis patients. However, the time-kinetic transition between effective anti-inflammatory therapies and regression of AA amyloid deposits remains uncertain. Here, we report a RA patient with systemic reactive AA amyloidosis who was successfully treated with prednisolone and etanercept, showing marked regression of gastroduodenal mucosal amyloid deposits within only 4 months. This is the first case report of RA-related systemic reactive AA amyloidosis histopathologically demonstrating rapid regression of amyloid deposits on gastroduodenal mucosa after adequate suppression of the underlying inflammatory condition.