Thistle - in their first season back among Scotland's elite clubs - secured their top-flight status after overcoming Hearts in a compelling 4-2 win at Tynecastle.
The Maryhill outfit had been staring at the prospect of needing to take something from their final game of the season against Ross County on Saturday after twice going behind to Callum Paterson and Danny Wilson goals at Tynecastle.
But Lyle Taylor and Gary Fraser cancelled out those efforts, with Lee Mair and Kallum Higginbotham wrapping up the victory.
The result lifts Partick up to seventh place and they can now enjoy Saturday's match as Hibernian and Kilmarnock lock horns in a shoot-out to avoid the relegation play-off place.
Archibald said: "It's bigger than anything I've done as a player, the lads have been a credit to themselves.
"It was a massive relief, the first emotion is relief. I'm just glad to get over the line because I don't envy those managers that are involved in it.
"It's hard to put into words what it means to stay in the league, I've been here through relegations and it's horrible, it affects everybody at the club and it affects everything you do.
"It's massive and I think the fans deserve it at this club.
"You work hard all year and try to play the right way to stay in the league, and I thought we did that."
Thistle went in at the interval 2-1 down but Archibald was delighted with the response after the break.
He added: "We told them at half-time that they had let themselves down and I think they knew that themselves, we didn't pass the ball in the first half. The second half was much more like them."
Partick inflicted relegated Hearts' first defeat in seven games but manager Gary Locke, whose side finish the season away to St Mirren on Saturday, was philosophical about the loss.
He said: "Credit to Partick, they deserved it. They played really well in the second half and battled really hard.
"You could see by their reaction at the end they were delighted.
"We are disappointed to lose but in the main I think the players deserve enormous credit, they have been fantastic over the last couple of months.
"But I thought they were a wee bit tired towards the end which is understandable with such a young side."