[2] The company was founded in 1970 by Bruce Thompson and Frederic D. Wolfe as the first healthcare focused real estate investment trust.

[9][10] The company invested about $5 billion in 2012; it primarily targeted private-pay senior housing and medical office buildings.

[11] On January 8, 2013, the company acquired nearly all the real estate assets of Sunrise Senior Living in a transaction valued at $4.3 billion.

In a related deal, Sunrise's property management business was recapitalized and spun-off to a partnership including Kohlberg Kravis Roberts, affiliates of Beecken Petty O'Keefe & Company, and Coastwood Senior Housing Partners LLC for $130 million.

HCN bought out their interests in late 2014 through a joint venture with Canadian senior living operator Revera, with Revera owning a 76% equity interest in the Sunrise Senior Living real estate management and the remainder owned by Welltower.

The company bought a 75% interest in the approximately CAD$1.35 billion portfolio with Revera owning the remaining 25%.

[14] In August 2015, Welltower formed a joint venture with the Canada Pension Plan Investment Board (CPPIB) to acquire a combined interest of 50.5% in a portfolio of medical office buildings in Southern California.

[15] Welltower announced an agreement to buy 19 properties from Vintage Senior Living for $1.15 billion in August 2016 and closed in September of the same year.