The barnstorming left winger produced the match-winning try with 12th minutes remaining with Australia behind 37-36.
A wide shift from outside their own 22 to the left put Lancaster down the edge, he rounded Fiji’s defence to score untouched under the posts before a final penalty goal put the game out of Fiji’s reach.
Australia were made to work for the result after Fiji hit back at opportune times just as the Junior Wallabies looked like running away with the game.
Lancaster’s first try, cutting back inside traffic after a Taj Annan offload and deft hands from No 8 Leafi Talataina, gave Australia a 17-13 lead which quickly became 24-13 after another try to centre David Vaihu.
Head coach Nathan Grey praised his side for sticking with their game plan which in the end proved too much for the Fijians.
“It was a fantastic game of footy with lots of tries scored and we’re very happy that we were able to get away with a win. We stuck to our playing style and we were able to get over the line.
“Our attacking ruck was pretty strong; our ball carriers were sometimes too good – we’ve got to speed up our support to make sure we don’t turn those balls over. And maintain our playing style, when we do that we can put teams under pressure and score points.”
Despite being down to 14 men, Fiji responded right on halftime to trail 24-20 at the break.
Australian wing Ronan Leahy struck early in the second half only for Fiji to respond quickly through Kavaia Tagivetaua.
A red card to prop Marley Pearce threatened to derail Australia’s match as Fiji then took the lead through Nakalevu and a penalty goal took the lead out to 37-29.
The Junior Wallabies needed to respond and reserve flyhalf Jack Bowen was instrumental in bringing Australia home.
Bowen put Melbourne Rebels fullback Mason Gordon over and then converted the try, before linking up with Lancaster for the game-winner.
Captain Nick Baker was happy to come out of the ‘dogfight’ with a result to keep their title hopes alive.
“It was sort of 50-50 at times but we sort of stuck through to the 80th minutes, and finally got that kick in the last 10 minutes that put us over the line. It was a bit of a dogfight but we got there in the end.”