Norwich ace Webster had thought his chance to qualify from Group D had passed when he lost 5-1 to Daryl Gurney in their final round-robin match at the Wolves Civic.
However, Webster had finished level on points and leg difference with namesake Mark Webster, who lost out 5-2 to Danny Noppert as the Dutchman claimed a consolation win from their final group game.
The duo returned to the stage to compete in a nine-dart shoot-out, with Mark Webster scoring a 140 with his first three darts and 298 in total, only to see Darren Webster land a treble 19 with his final dart to total 301.
"I'm really chuffed to get through, over the moon," said Webster. "It was hard for us both and to be honest I thought I was knocked out earlier on when I'd lost.
"I'm sorry for Mark because it was tough for us both. It's great to see him getting back to his best and he'll be back, but I'm pleased to have got through.
"I've got to refocus now for the second round but I know I can beat anyone and I've got to do something to take my practice game onto stage."
Gurney topped Group D with a third impressive victory of the group stage as he produced another strong performance.
"I wanted to get the win and to top my group and I'm delighted to have done that," said Gurney, who averaged 99 and hit five doubles from eight attempts. "I'm loving it and it's great to win my group in my first time here.
"My sole focus was getting the win and I had no idea of what had to happen in relation to Darren and Mark, Darren had some darts at a double that he didn't take and I hit some crucial finishes there.
"I'm very pleased with how I've been playing because I was nervous with the short format, but now I want to relax and play my best game."
Two-time Grand Slam of Darts finalist James Wade secured qualification from Group C alongside Phil Taylor with a 5-3 win over the six-time Wolverhampton champion in their decisive clash.
Following a defeat for Robbie Green against BDO World Trophy winner Peter Machin in their earlier match, Wade knew that he needed to defeat Taylor to progress and showed his quality to do just that.
The left-hander punished missed doubles from Taylor as he came from a leg down to lead 2-1 and 4-2, and though the 57-year-old kept the game alive it was Wade who sealed victory in style with an 11-darter.
"After losing my opening game on Saturday I'm pleased to have got through," said Wade. "Phil wasn't at his best but I came good for the last few legs.
"I think my last three legs were good enough to beat most players under pressure and at moments the practice I've been doing started to show."
Reigning champion Michael van Gerwen completed Group A with a third successive win, and was in dominant mood as he averaged 108.29 as he defeated Joe Murnan 4-2.
Murnan landed a 119 finish as he shared the opening four legs in his search for a consolation victory, but Van Gerwen took out 135 for a 12-darter before punishing two missed doubles from his opponent in leg six as he raced away to victory.
"There was not a lot of a pressure on me because I was through before the game, but I still wanted to win to keep my confidence up and I'm happy with this performance," said Van Gerwen.
"I played well and had a couple of nice finishes. I can still improve but I performed really well today."
Rob Cross secured qualification alongside Van Gerwen from Group A as he claimed a 5-2 win over Ross Montgomery in their decisive clash.
Montgomery took the game's opening leg and was level following four legs, but Cross took command with an 11-darter, took out 88 for a two-leg cushion and sealed his second round spot in style with a 164 checkout.
"I knew I had to win tonight to get through and it's lovely to get over the line," said Cross. "Ross is a great player and he's been a bit unlucky because he played well against Michael and me, but it's all about winning.
"My finishing was good in stages, I’m glad just to get over the line and get the win.
"It's been fantastic so far this week. The crowd all love the darts and it's been a massive experience for me, I'm looking forward to going into the knockout stages."
Raymond van Barneveld and Steve Lennon qualified from Group B after local star Jamie Hughes' consolation 5-1 victory over Gerwyn Price eliminated the Welshman.
Van Barneveld later defeated Lennon 5-2, with the Irish youngster landing two 100 finishes only to see the 2012 Grand Slam of Darts champion land five doubles from as many attempts, including a 160 checkout, in a perfect display.
"I'm happy to be through and to win my group is good," said Van Barneveld. "The aim for me was to win and I wanted to make sure I did that.
"The 160 finish was lovely and I needed it because Steve has played well and he's a good young player, so I'm pleased to beat him."
Tipton's Hughes finished his campaign on a high with a strong performance as he erased the memory of defeats to Van Barneveld and Lennon.
"I really enjoyed it tonight - there was no pressure and that showed in my performance," said Hughes. "It's nice for me to play well and win in front of my own fans here.
"I didn't realise that I'd knocked Gerwyn out, and I just wanted to go up there and play like I can do.
"The group stage makes this tournament so intriguing and Gerwyn will come back stronger - he's part of the new breed of players and his future is bright."
Following Tuesday's dramatic night, reigning champion Van Gerwen now progresses to face Lennon, Van Barneveld takes on Cross, Taylor plays Darren Webster and Gurney meets Wade in Thursday's second round.
The second round commences on Wednesday with the first four matches, including number two seed Peter Wright's clash with Stephen Bunting, Gary Anderson's tie against Michael Smith, Glen Durrant against Dave Chisnall and Mensur Suljovic taking on Berry van Peer.
Tickets for the bwin Grand Slam of Darts are available through www.wolvescivic.co.uk or by calling 0870 320 7000.
bwin Grand Slam of Darts
Tuesday November 14
8x A-D Group Matches
Danny Noppert 5-2 Mark Webster - Mark Webster and Darren Webster will play a nine-dart shoot-out
Daryl Gurney 5-1 Darren Webster - Daryl Gurney qualifies from Group D. Mark Webster and Darren Webster will play a nine-dart shoot-out
Michael van Gerwen 5-2 Joe Murnan - Michael van Gerwen qualifies from Group A
Rob Cross 5-2 Ross Montgomery - Rob Cross qualifies from Group A
Peter Machin 5-3 Robbie Green - Robbie Green is eliminated alongside Peter Machin
James Wade 5-3 Phil Taylor - Phil Taylor and James Wade qualify from Group C
Jamie Hughes 5-1 Gerwyn Price - Gerwyn Price is eliminated alongside Jamie Hughes
Raymond van Barneveld 5-2 Steve Lennon - Raymond van Barneveld & Steve Lennon qualify from Group B
Darren Webster 301, Mark Webster 298
Wednesday November 15 (7pm)
Second Round x4
Mensur Suljovic v Berry van Peer
Glen Durrant v Dave Chisnall
Gary Anderson v Michael Smith
Stephen Bunting v Peter Wright
Thursday November 16 (7pm)
Second Round x4 - Order of Play TBC
Michael van Gerwen v Steve Lennon
Raymond van Barneveld v Rob Cross
Phil Taylor v Darren Webster
Daryl Gurney v James Wade
Second Round - Best of 19 legs