Scotland coach Gregor Townsend announced his squad on Wednesday with Burke, who now plays for Saracens in the Premiership, a surprise inclusion to contest the first five-eighths role with Finn Russell and Tom Jordan.
Burke played 42 games for the Crusaders from 2020-24, scoring 134 points) and 37 times for Canterbury between 2019-24 (389). He has played 10 times for Saracens and has scored 71 points.
Burke, 25, qualifies for Scotland through his grandfather but was also considered by England, where he qualified through his mother.
Townsend said he expects Burke, a former New Zealand Under-20 representative, to make an immediate impact with Scotland.
"He's been on the radar for a while. I chatted with Fergus before he signed up for Saracens.
"He knew he was close to our squad, but he's only been offered a place earlier this week.
"You'd probably have to ask him when he made the decision. He's only had to make that decision in the last few days.
"When I asked him on Monday if he would commit to Scotland, he said yes. He didn't need to be asked twice or say, 'I'll get back to you tomorrow'. He said it would be a privilege.
"We've known about his Scottish heritage for two or three years now. We've kept in touch. He was in consideration in November, but we didn't feel his game at that time got him into our squad. He's playing better and better the more he plays.
"There is an opening in our squad with Adam [Hastings] getting injured too. So it was the right time for him. He's someone that understands the game from an attacking perspective.
"He's playing regular rugby at a top team with Saracens. He's a very good defender and can also play fullback."