Bramah House - an office building on Bermondsey Street - has changed hands for £14.25 million.
Toronto-based life assurance company Canada Life has bought the building from Hermes Investment Management.
Hermes payed just £5.6 million for the building in December 2011.
Chris Taylor of Hermes Investment Management said: "The sale of Bramah House, Bermondsey is an excellent result for the fund and follows four and a half years of asset management which has seen the value of the property almost triple. As a consequence we felt it was now the right time to dispose of the asset and explore other similar opportunities."
Canada Life's Michael White said: "We are very pleased to add Bramah House to our London portfolio.
"South Bank East is a strong and emerging central London office sub market. Completion of the extensive works to London Bridge will open up Bermondsey to the south of the station and we believe will strengthen future growth potential."