A 43-year-old man with ankylosing spondylitis (AS) was admitted with proteinuria and renal insufficiency. Coincidental IgA nephropathy and secondary renal amyloidosis were diagnosed on renal biopsy. This is the first case reported of coincidental IgA nephropathy and renal amyloidosis as a cause of renal insufficiency in a patient with AS. Both entities should be considered in the diagnosis in a patient with AS and renal impairment. A careful study of the renal tissue including, Congo red stain and immunofluorescence studies is necessary to establish a correct diagnosis in these patients.