AARP 601 E Street, NW Washington DC 20049. A note about our address. There are a number of P.O. boxes in Long Beach, California, associated with AARP’s Membership Processing Center. If you are ever uncertain if mail from AARP is legitimate or not, please contact us at 1-888-OUR-AARP (I-888-687-2277) and we’ll be happy to help.