Albion's 2-2 draw with QPR on Wednesday night proved enough to secure second place in the Championship and automatic promotion, with rivals Brentford losing 2-1 to Barnsley.
And after congratulating each other on the pitch, the players went outside to salute the large crowds who had gathered to celebrate the club's return to the top flight for the first time since the 2017/18 season.
Hundreds of supporters congregated on the car park next to the Astle Gates and nearby Birmingham Road, with one group of men stood on top of a merchandise kiosk and many blue and yellow smoke bombs let off.
WATCH: Footage shows Hawthorns celebrations:
Members of the squad including goalscorer Callum Robinson came out onto the car park to greet the supporters and sang along with fans from a nearby doorway into the stadium.
Supporters who attended the celebrations have now been urged to avoid any vulnerable people after a recent spike of coronavirus cases in the area.
Earlier nearby pubs were packed as fans anxiously watched a dramatic match of twists and turns as the final round of fixtures were played simultaneously. The Baggies came back from 1-0 down to lead 2-1 before drawing 2-2 as a late Barnsley goal confirmed Brentford's position in the play-offs.
Fans who partied outside The Hawthorns urged to avoid vulnerable people
It means West Brom will definitely renew their league rivalry with Wolves and potentially with Aston Villa, should the Birmingham club still be in the Premier League after the final round of fixtures on Sunday.
The director of public health at Sandwell Council, Dr Lisa McNally, had urged supporters not to celebrate in large groups but said today that it was inevitable some people would gather despite the Covid-19 risk.
Sandwell has had infection rates that 10 times higher than a few weeks ago and on Wednesday evening it was announced that West Bromwich firm CBS Packaging has closed for a fortnight after 49 out of 117 members of staff tested positive for Covid-19.