QuickLinks -- Click here to rapidly navigate through this document

Filed Pursuant to Rule 424(b)(3)
Registration No. 333-186788

(To prospectus and prospectus supplement each dated February 22, 2013)


        This prospectus supplement amends and supplements, and should be read in conjunction with, the prospectus dated February 22, 2013, as supplemented by the prospectus supplement dated February 22, 2013. The purpose of this supplement is to disclose amendments to our Dividend Reinvestment and Stock Purchase Plan (the "Plan") that have been approved by our Board of Directors pursuant to authority provided in the Plan.

        The following disclosure replaces the section entitled "Optional Investments in Excess of Plan Limits" on page S-8 of the prospectus supplement dated February 22, 2013. A copy of the complete prospectus, as amended and supplemented, may also be obtained from the Plan Administrator upon request.

Waiver Requests within an Announced Waiver Discount Period.

        Optional cash investments of more than $50,000 per month (including any initial investments in excess of $50,000) ("Large Cash Purchase") may be made only by investors that submit a request for waiver. Large Cash Purchase requests may be approved by us in our sole discretion at any time.

        Submission of Requests for Waiver.    Investors who wish to make Large Cash Purchases for any month should telephone Wells Fargo Shareowner Services at 1-877-218-2434 or Realty Income at 1-855-204-9800 or access Realty Income's corporate website to determine if we will be considering Large Cash Purchase requests for such month. When you inquire, you will be informed of one of the following:

        Large Cash Purchase request forms may be obtained online through our website at www.RealtyIncome.com/WaiverRequest or by requesting a copy by calling Wells Fargo Shareowner Services at 1-877-218-2434. We must receive completed Large Cash Purchase requests by delivery to Waiver-Discount@RealtyIncome.com by no later than 1:00 p.m. Pacific Time on the third business day before the first day of the "pricing period" for the applicable waiver period, as described below. We will notify by return email or by telephone any investor whose Large Cash Purchase request has been approved (including the amount of the investment approved) by 1:00 p.m. Pacific Time on the second business day before the first day of the applicable pricing period. The Plan Administrator must receive good funds relating to any approved Large Cash Purchase request by wire transfer to the account designated by us no later than 12:00 p.m. Pacific Time on the business day before the first day of the applicable pricing period. All such funds received after 12:00 p.m. Pacific Time on such business day may be returned without interest.

        Action on Large Cash Purchase Requests.    We have the sole discretion to grant or refuse to grant, in whole or in part, a Large Cash Purchase request. In acting on a Large Cash Purchase request, we will consider relevant factors, including without limitation:


Large Cash Purchases will be priced as follows:

Except as provided below, any trading day for which such volume weighted average price is less than the applicable threshold price will not be considered a Purchase Date, and no funds will be invested in shares of common stock on that date. Funds that are not invested will be returned without interest, as described below.


        From time to time, financial intermediaries, including brokers and dealers, and other persons may engage in positioning transactions in order to benefit from any waiver discounts applicable to investments made pursuant to requests for waiver for Large Cash Purchases under the Plan. Those


transactions may cause fluctuations in the trading volume of our common stock. Financial intermediaries and such other persons who engage in positioning transactions may be deemed to be underwriters. We have no arrangements or understandings, formal or informal, with any person relating to the sale of shares of common stock to be received under the Plan. We reserve the right to modify, suspend or terminate participation in the Plan by otherwise eligible persons to eliminate practices that are inconsistent with the purpose of the Plan.

        We may alter, amend, supplement or waive, in our sole discretion, the time periods and/or other parameters relating to optional cash purchases in excess of $50,000 made by one or more participants in the Plan or new investors, at any time and from time to time, prior to the granting of any request for waiver.

        Investing in our common stock involves risks. See "Risk Factors" beginning on page S-1 of the prospectus supplement dated February 22, 2013 and in our periodic reports and other information we file with the Securities and Exchange Commission.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

        The date of this prospectus supplement is November 21, 2013.