A gutsy all-round performance from the team, led by captain and player of the match Solofuti Falo, saw Samoa claim their first win by 30 runs over Fiji.
Fiji sent Samoa in to bat and continued their good form with the ball, tying the home team down by taking regular wickets.
Lasarusa Veiqaravi (4/22 off 7 overs) had an outstanding game with the ball taking four successive wickets in the middle of the innings.
Sitanisilao Toutai (15 off 87 balls) and number 11 Lester Evile (15* off 22 balls) were the only Samoan batsmen to trouble the scoreboard as they were bowled out for just 110 in 43 overs.
However Samoa's bowlers were spurred on by a vocal crowd to achieve what they needed to do.
The total appeared to be within reach for Fiji but some poor shot selection combined with tight bowling meant pressure began to mount.
As the wickets began to tumble, Samoa's confidence grew and when the sixth wicket fell with just 51 runs on the board, victory seemed within grasp.
Petero Cabebula (25* off 21 balls) offered some late resistance but in the end ran out of partners.
Falo was exceptional with the ball taking the last three wickets to get his team their first win.
Speaking after the match the Samoa captain was clearly pleased with the result and his team's performance.
"I feel so happy and the people in my country are so happy because this is the first time that we have ever won in the under 19 tournament," he said.
In the other match of the day Vanuatu looked to be on their way to their first win over Papua New Guinea at this level in many years, before a late batting collapse saw the PNG Garamuts get the win by 31 runs.
The result means PNG need to win only one of their next three games to book their place in the 2018 ICC Under 19 Cricket World Cup.
Post-match PNG captain and player of the match Vagi Karaho was happy with the result but acknowledged the team still has some work to do.
He believes that "with our batting, the mindset was not there and we need to be more mature with our batting."
After winning the toss and batting first, PNG would have been disappointed to be bowled out for just 136 in the 43rd over.
Karaho (24 off 63 balls) was the only batter who looked set to stay there from the PNG top five and knows that the team will have plenty to work on with their batting should they make the World Cup.
For Vanuatu, Obed Yosef (4/28 off 10 overs) had his first excellent performance for the tournament although their bowlers would come to regret the 30 extras they gave PNG.
The Garamuts were on the back foot with Vanuatu cruising at 4 for 80 in the 25th over, but the team rallied around each other to show they are on top of the table, taking six wickets for just 25 runs to get the win.
James Junior Tau (3/27 off 8 overs) remains the pick of the swing bowlers at the tournament while three other bowlers each picked up two wickets for PNG.
Despite remaining undefeated captain Karaho knows that "the most important thing for us is to keep our minds switched on and not relax because there's a long way to go."
The second round of the tournament starts on Sunday.
PNG face Fiji in a vital rematch while Samoa will be looking to get their second win when they take on Vanuatu.
The top team will qualify for the 2018 ICC Under 19 Cricket World Cup to be held in New Zealand in January 2018.