Reedie, a 72-year-old Scot, becomes the third president of WADA, which was set up by the IOC in 1999 to lead the global fight against doping.
The presidency rotates between national governments and the Olympic movement. Canadian IOC member Dick Pound served as WADA's first president from 1999 to 2007.
Reedie, a member of WADA's executive committee and foundation board, has also served as chairman of its finance committee.
"I like to think that I know a little bit about national anti-doping organizations," Reedie said, before adding jokingly: "I can confirm to you that I was an athlete and to the best of my knowledge I never tested positive."
Reedie backed the tougher sanctions for cheats after WADA doubled the bans from two years to four, a key change to the new World Anti-Doping code approved earlier Friday in Johannesburg.
"This code is the accumulated wisdom of the anti-doping world. ... I certainly hope that the higher sanctions become a much more regular fact of life," he said.
Reedie is the former head of the British Olympic Association and the International Badminton Federation.
His election was welcomed in Britain by the U.K. Anti-Doping agency.
"The challenge for him over the next few years is to bring the public and sporting authorities closer together, and to lead the evolution and strengthening of compliance with the new code," UKAD chief executive Andy Parkinson said.