The franchise has signed lock Brad Thorn, loose forward TJ Ioane and first five-eighth Hayden Parker for next season while Christie comes south from the Crusaders.
With Parker signed for next season and Lima Sopoaga also heading back to the Highlanders, that signals Colin Slade is on his way back to the Crusaders.
Highlanders coach Jamie Joseph said he was pleased to have signed the players and the squad for 2014 was taking shape.
Thorn will be 39 when the competition kicks off next season but he shows no sign of slowing down and his experience is greatly valued by Joseph.
''It's great to have Brad on board for 2014 as he brings a great deal of professionalism to any team he plays for. His work ethic, experience and leadership are invaluable for our team and he has been one of the most consistent players this season,'' Joseph said.
He will have a complete break from playing for the next few months before beginning pre-season training with the Highlanders in November.
Parker (22) has had an impressive first year, especially with his goal kicking, and returns for a second season.
Ioane (24) was originally not named in the 32-man squad, or the wider training squad, this season but was called into the team after early-season injuries, and has impressed with his hard-running and high energy game.
Christie comes to the team after playing well for Tasman over the past couple of seasons. He was named in the Crusaders this season but played only one game, due to injury and the consistent form of Matt Todd ahead of him.
The selection of the 28-year-old means the future of other openside flankers such as Tim Boys and Huge Blake is clouded.
Tamati Ellison has signed for Japanese club Ricoh but is seeking a clearance from the New Zealand Rugby Union to come back and play for the Highlanders next season. He would be classed as an overseas player.
Approval for Ellison to come back next season will by decided by the NZRU at a board meeting next month.
With the signings Joseph said he had the core of his squad for next year but was looking out for players who perform well in this year's ITM Cup.
He has more than 20 players locked up for next season.
Highlanders general manager Roger Clark said the signings of the players, along with the signature of fullback Ben Smith earlier this month, meant plans were on track to move onwards and upwards after a disappointing 2013 season.