Gordon thus ends his Glasgow attachment, which began in the amateur era.
He has played 138 games for Glasgow in the team's current format since 1998. Before that he had 29 appearances for the district in the early years of professional rugby, making his Glasgow debut in 1995 against Griqualand West, the South African Currie Cup team.
Gordon, who won his 75th cap against England two months ago, said: "I have had 10 years with Glasgow Rugby in one guise or another, and, like all good things, it has come to an end. I'm very much looking forward to the Lions tour and then all the excitement that joining a club with the drive and ambition of Leeds Tykes will bring.
"Obviously it's hard to leave my home city, and I'd like to thank my agent, Shaun Longstaff, for all he's done to secure this opportunity for me."
Richie Dixon, Scotland's acting Director of Rugby, who coached Bulloch at both international and pro-team level, said: "Gordon has given 10 years of dedicated service to Glasgow Rugby, and he has been an outstanding personality for Scottish Rugby. I wish Gordon all the very best in his move to Leeds and look forward to his continuing contribution to Scottish Rugby."
Phil Davies, Leeds Tykes' Director of Rugby, added: "Gordon is a world-class player who has performed at the highest level. At 30, Gordon is still in his prime as a front-rower, and we are excited about him joining our current group of players and adding his experience to the blend that we already have."