The game was played one day later than originally scheduled after the severe storms that came through the metro-Atlanta area forced its postponement Wednesday.
The teams traded goals to tie the game at 2-all at halftime before Region 5AAAAA champion Lassiter (17-0-1) scored three unanswered goals in the second half to put the game away and advance. The Trojans will host Brookwood on Wednesday.
Alex Hanks, Shaban Abousaud, Tyler Happ, Drake Dinnan and William Robinson scored one goal each for the Trojans.
It was a far from easy start to the state playoffs for Lassiter as North Gwinnett (11-8), the fourth seed from 7AAAAA, played aggressively from start to finish. The Bulldogs' Matthew Melton and Roberto Hinojosa - who each scored a goal - proved particularly troublesome for the Trojans.
"We knew coming into this match that they were going to come at us - they were going to pressure," Lassiter coach Billy Pritz said. "(Melton) and (Hinojosa) were giving us problems all night. We watched film on them and we talked about it at halftime and sorted it out."
North Gwinnett coach Michael Wentzler was proud of how competitive his players were against the state's top-ranked team.
"We came in playing the No. 1 team, had an unlucky draw with our 4 seed after finishing strong in the region, but they played very well," Wentzler said. "We had a plan, we stuck to it. We had some breakdowns and Lassiter is a very good team. They took advantage of those. They put away the chances they created and we let them have."
Lassiter got on the scoreboard fairly quickly as Hanks scored from short distance off of a cross from Drake Dinnan less than 5 minutes into the game to give the Trojans a 1-0 lead.
North Gwinnett eventually struck back when Hinojosa scored from close range to tie the game at 1-all with 19:28 left in the first half.
It didn't take long for Lassiter to respond, however, as Abousaud kicked the ball away from North Gwinnett goalkeeper Michael Hennessey, who was about to grab it on the bounce, and deposited it in the goal to put the Trojans back ahead 2-1 with 12:25 left.
Lassiter nearly increased its lead to 3-1 at the beginning of the second half, but Tyler Happ's goal off of a cross by Abousaud was waived off on an offsides call.
Instead, the game ended up tied again as Melton scored from close range to even the score at 2-all with 34:45 left.
Lassiter responded a little over 2 minutes later when Happ blasted the ball into the goal on an assist from Abousaud to give the Trojans a 3-2 lead.
Lassiter followed that up with several scoring attempts that fell short. North Gwinnett also had a couple of missed shots before Dinnan scored to increase the Trojans' advantage to 4-2 with 13:15 left.
Robinson gave Lassiter its final goal of the game as he took a pass from Happ, who faked a shot on a free kick, and scored with 1:53 left to give the Trojans their final margin of victory.
"We talked about the five steps in the playoffs, and this was step one, and we accomplished our goal," Pritz said. "We always want to keep a shutout, but we knew it was going to be tough to hold this attacking team, North Gwinnett, back. I'm proud of my guys. They showed a lot of resolve, managed the game once it was in hand and we're looking forward to Brookwood next week."