| Result | Tournament |
|---|---|
| Mark Tucker defeated Mark O'Sullivan | 1998 UK Tour - Event 1 Snooker |
| Jason Curtis defeated Mark O'Sullivan | 1997 World Championship Snooker |
| Paul Sweeny defeated Mark O'Sullivan | 1996 World Championship Snooker |
| Gary Ponting defeated Mark O'Sullivan | 1996 Welsh Open Snooker |
| Mark O'Sullivan defeated Adrian Gunnell | 1996 Welsh Open Snooker |
| John Whitty defeated Mark O'Sullivan | 1996 UK Championship Snooker |
| Steve Archer defeated Mark O'Sullivan | 1996 Thailand Open Snooker |
| Karl Broughton defeated Mark O'Sullivan | 1996 International Open Snooker |
| Mark O'Sullivan defeated Damian Massey | 1996 International Open Snooker |
| John Read defeated Mark O'Sullivan | 1996 Grand Prix Snooker |
| Mark O'Sullivan defeated Simon Smith | 1996 Grand Prix Snooker |
| Joe Jogia defeated Mark O'Sullivan | 1996 European Open Snooker |
| Peter Lines defeated Mark O'Sullivan | 1996 British Open Snooker |
| Mark O'Sullivan defeated Roy Bigg | 1996 British Open Snooker |
| Steve Archer defeated Mark O'Sullivan | 1995 World Championship Snooker |
| Nick Pearce defeated Mark O'Sullivan | 1995 Welsh Open Snooker |
| Mark O'Sullivan defeated Alistair Fleming | 1995 Welsh Open Snooker |
| Robin Hull defeated Mark O'Sullivan | 1995 UK Championship Snooker |
| Mark O'Sullivan defeated John Dunning | 1995 UK Championship Snooker |
| Fergal O'Brien defeated Mark O'Sullivan | 1995 Thailand Open Snooker |
| Mark O'Sullivan defeated Steve Harrison | 1995 Thailand Open Snooker |
| Mark O'Sullivan defeated Craig Edwards | 1995 Thailand Open Snooker |
| Mark O'Sullivan defeated Glenn Stevenson | 1995 Thailand Open Snooker |
| Mark O'Sullivan defeated David Thompson | 1995 Thailand Open Snooker |
| Peter Daubney defeated Mark O'Sullivan | 1995 Thailand Classic Snooker |
| Mark O'Sullivan defeated Colm Gilcreest | 1995 Thailand Classic Snooker |
| Darren Lennox defeated Mark O'Sullivan | 1995 International Open Snooker |
| Mark O'Sullivan defeated Mark Williams (II) | 1995 International Open Snooker |
| Lee Richardson defeated Mark O'Sullivan | 1995 Grand Prix Snooker |
| Mark O'Sullivan defeated Joe Grech | 1995 Grand Prix Snooker |
| Mark O'Sullivan defeated Gary Peters | 1995 Grand Prix Snooker |
| Peter Lines defeated Mark O'Sullivan | 1995 German Open Snooker |
| Mark O'Sullivan defeated Andy Duff | 1995 German Open Snooker |
| David Singh defeated Mark O'Sullivan | 1995 British Open Snooker |
| Fergal O'Brien defeated Mark O'Sullivan | 1994 World Championship Snooker |
| Mark O'Sullivan defeated Cliff Wilson | 1994 World Championship Snooker |
| Mark O'Sullivan defeated Oliver King | 1994 World Championship Snooker |
| Mark O'Sullivan defeated Shokat Ali | 1994 World Championship Snooker |
| Mark O'Sullivan defeated Matt Gibson | 1994 World Championship Snooker |
| Mark O'Sullivan defeated Jamie Bodle | 1994 World Championship Snooker |
| Mark O'Sullivan defeated David Thompson | 1994 World Championship Snooker |
| Joe Grech defeated Mark O'Sullivan | 1994 Welsh Open Snooker |
| Mark O'Sullivan defeated Colin Roscoe | 1994 Welsh Open Snooker |
| Mark O'Sullivan defeated Kevin Ashby | 1994 Welsh Open Snooker |
| Mark O'Sullivan defeated Nic Barrow | 1994 Welsh Open Snooker |
| Mark O'Sullivan defeated Philip Williams | 1994 Welsh Open Snooker |
| Jim Chambers defeated Mark O'Sullivan | 1994 UK Championship Snooker |
| Mark O'Sullivan defeated Edvard Matthiasson | 1994 UK Championship Snooker |
| Mark O'Sullivan defeated Andrew Alexandrou | 1994 UK Championship Snooker |
| Ryan Milton defeated Mark O'Sullivan | 1994 Thailand Open Snooker |