It was an excellent first day for the Welsh players, as Jak Jones, Dylan Emery and Mark Williams all won their first-round matches.
Jones took a comfortable 4-1 win over England’s Liam Highfield, while Emery shocked China’s Lei Peifan with a deciding-frame victory.
Home favourite Williams – who was the last Welsh player to win the title back in 1999 – overcame Michael Holt to win 4-2 and set up a second-round match against Martin O’Donnell.
O’Donnell upset 25th seed Tom Ford 4-2 later on Monday.
England’s Robbie Williams knocked out world number 16 Si Jiahui with a 4-2 win.
Williams will face last year’s runner-up and former Welsh Open winner Stephen Maguire in the second round after his come-from-behind win over Ricky Walden.
Barry Hawkins was forced to go the distance against fellow Englishman David Lilley, though the 12th seed came out on top with a 4-3 win, sealing his win with a 108 break in the decider.
In Monday’s evening session there were comfortable wins for Joe O’Connor, Wu Yize and two-time Welsh Open winner Neil Robertson.
The final two games of the day both produced surprise results, as David Grace knocked out eighth seed Mark Allen – who has not reached a Welsh Open final in his career – with a 4-2 win.
And Anthony McGill beat the 2009 Welsh Open champion Ali Carter in a deciding frame to book his place in the second round.
The pair will face Monday’s Welsh winners, with Grace playing Emery and McGill taking on Jones in the second round in Llandudno.