Born in Inverness, Heathcote won his first cap for the nation as a replacement in the 2012 EMC Test against Tonga at Pittodrie Stadium in Aberdeen.
He was selected in Scotland's 2013 RBS 6 Nations squad and subsequently started at stand-off for Scotland A, kicking eight points in the 13-9 win over England Saxons, the side's first win on English soil.
He then went on to make two starts for Scotland in the 2013 summer quadrangular tournament against Samoa and Italy, and is considered one of the brightest young contenders for the national number 10 jersey.
Tom Heathcote said: "I'm really excited about joining Edinburgh Rugby, to play for them in the PRO12 and European Rugby Challenge Cup, and to play where I want to be internationally.
"All in all I'm really looking forward to getting there and getting started.
"I've followed the club quite closely for a number of seasons and have seen the improvements made this year. I think it's a club that's in a good position to push on.
"Alan Solomons [head coach] has a really strong vision for the future. There's a lot of good young players that are expected to develop under him, which I think will take the club from strength to strength over the next few years.
"From my point of view, I've had about three years of Premiership experience, but am still quite young. I'm sure I'll keep developing as a player in a team that will continue to improve in the coming seasons, especially as that core of young players gets more game time and experience."
On leaving school in Salisbury, Heathcote was immediately snapped up by the Bath Academy and made his first team debut for the west-country club in 2011.
He was shortlisted for the 2013 LV= Breakthrough Player Award, after outstanding performances in the early stages of the competition.
He has gone on to score 257 points in 41 Premiership and European Cup appearances, and will now look to continue his development for the capital club in the PRO12.
Edinburgh Rugby head coach, Alan Solomons, said: "It's very pleasing to announce the signing of another quality, young - and in this case, experienced - Scottish player to our senior squad.
"Tom joins us with three seasons' experience in the English Premiership so I expect him to make a valuable contribution straight away.
"His arrival will certainly intensify the competition for places at pivot while, at just 22, he also fits well with our increasingly promising group of young Scots coming through at the club.
"It all bodes very well for the future of Edinburgh Rugby."
Tom Heathcote (22), stand-off
Born: 11/02/1992 in Inverness
Height: 5ft 10in (1.80m); weight: 14st (90kg)
Guinness PRO12
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The Sweepstakes
Ballsbridge, Dublin 4, Ireland