Gatland knocked over the winning dropped goal in the 28-27 cliffhanger win over the Chiefs at Forsyth Barr Stadium.
Gatland slotted what he admitted was a rather wonky effort with less than two minutes remaining from about 30m out.
It is the second time he has scored a match-winning dropped goal on the ground; he kicked one for his North Harbour provincial side in a championships final in 2016.
For Gatland it was just great to be back on the field.
"This week has been pretty strange for me. Got a late call in and minutes off the bench. It was my first game back after 13 months so I was just stoked to get out there. And to have that game finish like that was awesome," he said.
"Nerves build up to a game but you just have to back your ability and the things you know. I have been training for quite a while preparing for these type of times."
Gatland was called into the bench on Thursday after Josh Ioane pulled out with a groin strain.
"It was a wee bit wonky, a wee bit left to right. I was pretty lucky to knock it over. But credit has to go to the team and the way they performed."
His father, Warren, who coached the Chiefs, said afterwards Bryn had joked with him he would kick a dropped goal to win the match.
The Highlanders just shaded the contest which was dominated by the whistle, as referee Paul Williams handed out 30 penalties.
Tough new rules at the breakdown, which were supposed to quicken the game up, had the opposite effect as continuity was lost.
The Highlanders led 22-16 at the break, scoring three tries in the first half. Captain Ash Dixon, who had one of his best games in the Highlanders jersey, scored the first after a 15m lineout drive, and Sio Tomkinson got the next after centre Rob Thompson ran a great line. No8 Marino Mikaele Tu’u scored the third try for the Highlanders from a nice inside ball by Mitch Hunt.
The second half was dominated by the whistle and the Chiefs hung tough and went ahead with just over three minutes left as Damian McKenzie slotted what he thought was the winning dropped goal. But it was not to be as Gatland came forward.
Best for the Highlanders were Dixon, Thompson, and halfback Aaron Smith did some good things while the tight five impressed.
Highlanders v Chiefs
Highlanders 28 (Ash Dixon, Sio Tomkinson, Marino Mikaele-Tu’u tries; Mitch Hunt 2 con, 2 pen; Bryn Gatland d-goal)
Chiefs 27 (Sean Wainui, Anton Lienert-Brown tries; Damian McKenzie 4 pen, con, d-goal).
Halftime: 22-16
Crowd: 18,218