| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 1. A Lytchak vs A Keessen |
| 1-0 | 105 | 1996 | Hengelo U20 | A57 Benko Gambit |
| 2. A Keessen vs M van Essen |
| 1-0 | 42 | 1996 | Hengelo U20 | E98 King's Indian, Orthodox, Taimanov, 9.Ne1 |
| 3. M Dambacher vs A Keessen |
| 1-0 | 73 | 1997 | NED-ch U20 | A41 Queen's Pawn Game (with ...d6) |
| 4. A Keessen vs E Knoppert |
| 0-1 | 61 | 1998 | Haarlem AKN op | A58 Benko Gambit |
| 5. A Keessen vs Khenkin |
| 0-1 | 26 | 1998 | Haarlem AKN op | D30 Queen's Gambit Declined |
| 6. N Vink vs A Keessen |
| 0-1 | 28 | 1998 | NED-ch U20 | B65 Sicilian, Richter-Rauzer Attack, 7...Be7 Defense, 9...Nxd4 |
| 7. A Keessen vs J Willemze |
| ½-½ | 18 | 1998 | NED-ch U20 | A57 Benko Gambit |
| 8. A Keessen vs S de Boer |
| ½-½ | 61 | 1998 | NED-ch U20 | E91 King's Indian |
| 9. A Keessen vs M Dambacher |
| 0-1 | 37 | 1998 | NED-ch U20 | A10 English |
| 10. S Bakker vs A Keessen |
| 1-0 | 50 | 1998 | NED-ch U20 | A49 King's Indian, Fianchetto without c4 |
| 11. M Wunnink vs A Keessen |
| 1-0 | 43 | 1998 | NED-ch U20 | D91 Grunfeld, 5.Bg5 |
| 12. A Keessen vs L Zweedijk |
| 1-0 | 27 | 1998 | Hogeschool Zeeland Open | E91 King's Indian |
| 13. M Gurevich vs A Keessen |
| 1-0 | 36 | 1998 | Hogeschool Zeeland Open | A59 Benko Gambit |
| 14. A Keessen vs R Burgerhoff |
| 1-0 | 29 | 1998 | Hogeschool Zeeland Open | A10 English |
| 15. W Bliek vs A Keessen |
| 0-1 | 34 | 1998 | Hogeschool Zeeland Open | D90 Grunfeld |
| 16. A Keessen vs S Safin |
| 0-1 | 33 | 1998 | Hogeschool Zeeland Open | E94 King's Indian, Orthodox |
| 17. P Kalisvaart vs A Keessen |
| ½-½ | 41 | 1998 | Hogeschool Zeeland Open | B50 Sicilian |
| 18. A Keessen vs E van Driel |
| 1-0 | 59 | 1998 | Hogeschool Zeeland Open | E12 Queen's Indian |
| 19. A Keessen vs T Middelburg |
| ½-½ | 43 | 1999 | NED-ch U20 | D31 Queen's Gambit Declined |
| 20. J Berkvens vs A Keessen |
| 1-0 | 33 | 1999 | NED-ch U20 | B75 Sicilian, Dragon, Yugoslav Attack |
| 21. A Keessen vs J Amesz |
| ½-½ | 25 | 1999 | NED-ch U20 | A50 Queen's Pawn Game |
| 22. S Ernst vs A Keessen |
| 1-0 | 35 | 1999 | NED-ch U20 | A04 Reti Opening |
| 23. A Keessen vs J Jens |
| 1-0 | 46 | 1999 | NED-ch U20 | E98 King's Indian, Orthodox, Taimanov, 9.Ne1 |
| 24. N Vink vs A Keessen |
| 1-0 | 28 | 1999 | NED-ch U20 | B74 Sicilian, Dragon, Classical |
| 25. N Mitkov vs A Keessen |
| 1-0 | 27 | 1999 | Haarlem AKN op 8th | B35 Sicilian, Accelerated Fianchetto, Modern Variation with Bc4 |
Kibitzing
