Myners, who will replace Peter Birch as chairman next January, left M&S earlier this month. He was replaced by Lord Burns at the retailer's AGM on July 12.
Myners' move to Land Securities reunites him with M&S chief executive Stuart Rose, who has been a non-executive director at the firm since 2003.
Prior to joining M&S, Myners ran the fund manager Gartmore for 15 years. He is a member of the court of directors of the Bank of England and chairman of the Guardian Media Group and Tate.
Land Securities is a UK commercial property company with 30 shopping centres, 30 retail parks and 10 supermarkets across the country, as well as retail space in central London.