Full-back Morgan Stoddart scored a third-minute try that would have graced any game in the ground's 129-year history after a classical outside break from Kiwi centre Regan King.
Fly-half Stephen Jones added a penalty as early Scarlets pressure continued to tell and while under-strength Bristol battled bravely in defence this game was all about whether or not the hosts could live up to their illustrious reputation.
Simon Easterby's side did so in patches, but had to work hard for every inch of territory despite their overall superiority.
Easterby ploughed over in less-spectacular fashion than Stoddart after a determined Mark Jones break to which fly-half Stephen Jones added the conversion.
Fly-half Jones added a penalty nine minutes after the break and north Wales-born former Bristol player Rob Higgitt went over unopposed for the final try at the ground from Stoddart's one-handed pass.
Jones converted to claim the final points scored at the historic stadium.
Emotional scenes at Stradey swansong
Former Scarlets and Llanelli RFC captains paraded around the pitch before kick-off, the oldest being ex-scrum-half Handel Greville, 87, who led them in 1948-49.
There was a presentation to Gareth Jenkins, the ex-coach known around the world for his lifelong association with Stradey Park.
Afterwards Jenkins said: "It's absolutely fantastic, an absolutely wonderful occasion. We'll remember this night forever.
"It was the occasion we expected it to be. It was a good game, the crowd were magnificent and our heritage was on display.
"Many of the fantastic men of the past who created the tradition we're so proud of were here.
"It's had everything. What a fitting occasion to say so-long. What a wonderful night to celebrate what this place has been.
"This is as good as it gets. It's up there with the great occasions I've experienced at Stradey Park."
The capacity crowd filled the stadium with music with the help of singer Caryl Parry Jones, who performed West is Best, composed in memory of the late Llanelli, Wales and Lions centre Ray Gravell.
At the end two choirs, Cor Meibion Llanelli and the Scarlets Choir, sang the Stradey anthem Sosban Fach and the Welsh national anthem Hen Wlad fy Nhadau before a fireworks display brought an end to formal events.
I was privileged to have changed in that dressing room and run on to that field with some of the greatest players in world rugby history
Ex-Llanelli, Wales and Lions captain Phil Bennett watched as he celebrated his 60th birthday.
Legendary fly-half Bennett said: "I was privileged to have changed in that dressing room and run on to that field with some of the greatest players in world rugby history' and that will make me a very satisfied man.
"If we can take some of the great occasions and atmosphere from Stradey Park to Parc y Scarlets, then job done.
"My biggest wish is we take this unique atmosphere to the new stadium."
Bennett is ranked as one of the greats to have come from Stradey, having led Llanelli for six years during the most successful era in the club's history during the 1970s.
The mighty New Zealand All Blacks were felled there in 1972 and that stands out to Bennett as the greatest game to have been played at Stradey Park.
He said: "I've been very lucky. In 1970 Llanelli pushed the Springboks close at Stradey Park with a wonderful try by a man named Alan Richards, an old classmate of mine.
"Then I played in a game in 1972 and beat the All Blacks 9-3. That's gone down in folklore and for me that eclipses Grand Slams and Triple Crowns - for me that's the greatest ever game at Stradey Park."
Chief executive Stuart Gallacher said: "My biggest memory of Stradey Park? For me it has to be this occasion. After all those games, for me this is it. It's fantastic.
"I'm certain we can take the spirit of Stradey Park to Parc y Scarlets."
Llanelli, Wales and Lions legend Ieuan Evans said: "You could see how much it meant to so many people."
Scarlets: Stoddart; Higgitt, King, Evans, M Jones; S Jones, Martens; I Thomas, Owens, Meeuws, Cooper, Day, N Thomas, Easterby (c), Lyons. Replacements: Davies for G Evans (62), C Thomas for M Jones (67), Roberts for Martens (59), Rees for Owen (53), John for Meeuws (53), D Jones for Cooper (41).
Not Used: J. Edwards.
Bristol: Elliott; Robinson, Eves, Fatialofa, Turner; Ashwin, Thomas; Irish, Linklater, Crompton, Sambucetti, Sidoli, Salter, R Pennycook, Blowers. Replacements: Maggs for Fatialofa (58), Alford for Thomas (66), Blaney for Linklater (62), Bracken for Crompton (64), C Pennycook for Blowers (64).
Not Used: Attwood, Barden.
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