With Tonga Princess Latufuipeka Tuku'aho and Prime Minister Lord Fatafehi Fakafanua in attendance at Allianz Stadium, Tupou starred to keep the Roosters entrenched in the NRL's top four.
Without four of their State of Origin stars, the Tricolours were below their best and regularly wasteful of good ball in the first half while camped on the Eels' line.
Still it was Tupou who ultimately proved the difference, and he now looks every chance of becoming the third man to reach 200 career tries by year's end.
Off contract at the end of this season the 35-year-old is yet to confirm his future, but could go past Ken Irvine and sit behind only Alex Johnston on the all-time tryscoring list if he plays on in 2027.
After being forced to wait for his 300th game having injured his calf in May, Tupou had limited ball in the first half as the Roosters preferred to go right.
But with the scores locked at 6-6, he gave the hosts the advantage when he finished off a left-edge shift and got the ball down in the corner.
Tupou has always been a reliable finisher on the wing, but it is in the air where the he is at his best.
Some 62 of his 194 career tries have come from kicks, with two more on Saturday night sealing the game for the Roosters.
The flyer first jumped over Brian Kelly to claim a Hugo Savala bomb and make it 22-6 before he finished his hat-trick by running onto a Benaiah Ioelu grubber late.
"The first half we were a bit worried, but he rewarded us with three tries, congratulations. God bless you Daniel Tupou, go Roosters," Lord Fakafanua said after presenting Tupou with an engraved plaque.
Parramatta had been gutsy in the first half to only trail 4-0 at the break, and even led 6-4 early in the second when Jack Williams put Joash Papalii over.
But ultimately, weight of possession told with the Roosters having 63 per cent of the ball and playing with more control after the break.
Cody Ramsey looked dangerous with every run while filling in for James Tedesco as Roosters fullback, breaking the line twice and sending Billy Smith over for a try.
Spencer Leniu was powerful up front against an Eels pack he has been linked to joining next year, while front-row partner Naufahu Whyte was again immense.Â
Earlier, Mark Nawaqanitawase produced another miracle play for the highlights reel when he flung a ball back in-field for Robert Toia to score the Roosters' first.
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