Experienced star Beaton, the runner-up in 2014 European Tour event in Gibraltar, was facing a first-round exit for a second successive European Tour event when De Decker took a 4-2 lead in their clash.
The Belgian youngster had secured the game's first break as he moved out to lead 4-2, but crucially missed a dart at double-top to open up a three-leg gap and Beaton pounced to power to victory.
The former Lakeside world champion landed 180s in four successive legs as he swept past De Decker and moved through to meet Simon Whitlock in round two.
"I love it here and I'd love to still be in at the end of the weekend," said Beaton. "I'm really happy, I think I played quite well and that's a good result for me."
Christian Kist held off Ronny Huybrechts' comeback from 3-1 and 4-2 down to level at 4-4 before the former Lakeside champion pulled away for a 6-4 triumph, setting up a clash with Michael Smith in the second round.
Former European Tour finalist Paul Nicholson saw three match darts go begging in the deciding leg of his see-saw battle with Chris Quantock, who enjoyed his first win on the European Tour with a narrow 6-5 victory.
John Henderson landed a brilliant 170 finish during his 6-4 win over Germany's Rene Eidams but all five of the host nation's qualifiers bowed out.
Friday's first-round results
Afternoon Session
Jeffrey de Zwaan 4-6 Alan Tabern
Jonny Clayton 6-5 Justin Pipe
Richie Corner 5-6 Darren Webster
Matthew Dennant 1-6 James Richardson
Justin Broton 3-6 Matt Clark
Martin Schindler 6-4 Callan Rydz
Magnus Caris 6-1 Dyson Parody
Paul Nicholson 5-6 Chris Quantock
Evening Session
Mario Robbe 0-6 Rob Cross
Rene Eidams 4-6 John Henderson
Ritchie Edhouse 3-6 Krzysztof Ratajski
Steve Beaton 6-4 Mike De Decker
James Wilson 6-1 Dylan Duo
Christian Kist 6-4 Ronny Huybrechts
Manuel Vilerio 1-6 Darren Johnson
Dimitri Van den Bergh 6-2 Anthony Lopez
Saturday's second-round order of play
Afternoon Session (12pm-4pm BST)
Cristo Reyes v James Richardson
Daryl Gurney v Darren Webster
Alan Norris v Matt Clark
Benito van de Pas v Martin Schindler
Stephen Bunting v Chris Quantock
Jelle Klaasen v Magnus Caris
Michael Smith v Christian Kist
Joe Cullen v Rob Cross
Evening Session (6pm-10pm BST)
Gerwyn Price v Darren Johnson
Mensur Suljovic v Alan Tabern
Dave Chisnall v Jonny Clayton
Peter Wright v Krzysztof Ratajski
James Wade v Dimitri Van den Bergh
Kim Huybrechts v James Wilson
Ian White v John Henderson
Simon Whitlock v Steve Beaton
Click here for full results and schedule
