| Game |
| Result | Moves |
Year |
Event/Locale | Opening |
| 1. G Halldorsson vs A A Gretarsson |
| 1-0 | 27 |
1984 |
Reykjavik | B93 Sicilian, Najdorf, 6.f4 |
| 2. G Halldorsson vs L Shamkovich |
| ½-½ | 60 |
1984 |
It (open) | D85 Grunfeld |
| 3. Petursson vs G Halldorsson |
| 1-0 | 41 |
1995 |
Ch Iceland /96 Reykjavik (Iceland) | A10 English |
| 4. D Perry vs G Halldorsson |
| ½-½ | 39 |
1999 |
EM/MN/014 | B21 Sicilian, 2.f4 and 2.d4 |
| 5. G Halldorsson vs N Morihama |
| ½-½ | 41 |
1999 |
EM/MN/014 | D20 Queen's Gambit Accepted |
| 6. W Schmid vs G Halldorsson |
 | 1-0 | 27 |
1999 |
EM/MN/014 | B75 Sicilian, Dragon, Yugoslav Attack |
| 7. A Gunnarsson vs G Halldorsson |
| ½-½ | 15 |
2001 |
ISL-chT 2000/01 | B22 Sicilian, Alapin |
| 8. P Gengler vs G Halldorsson |
| 0-1 | 45 |
2008 |
Euro Club Cup | C01 French, Exchange |
| 9. G Halldorsson vs V Bucinskas |
| 0-1 | 33 |
2008 |
Euro Club Cup | D20 Queen's Gambit Accepted |
| 10. G Halldorsson vs M Perez Candelario |
| 0-1 | 48 |
2008 |
Euro Club Cup | D31 Queen's Gambit Declined |
| 11. Y Kryvoruchko vs G Halldorsson |
| 1-0 | 46 |
2008 |
Reykjavik Open | C03 French, Tarrasch |
| 12. T Cross vs G Halldorsson |
| 0-1 | 51 |
2009 |
Reykjavik Open | C03 French, Tarrasch |
| 13. G Halldorsson vs G Stern |
| 1-0 | 42 |
2009 |
European Club Cup | D35 Queen's Gambit Declined |
| 14. R Berg vs G Halldorsson |
| ½-½ | 34 |
2009 |
Reykjavik Open | C18 French, Winawer |
| 15. G Halldorsson vs S Ingason |
| 1-0 | 27 |
2009 |
Reykjavik Open | D11 Queen's Gambit Declined Slav |
| 16. R Van Wessel vs G Halldorsson |
| 1-0 | 72 |
2009 |
European Club Cup | A90 Dutch |
| 17. G Halldorsson vs D Tratatovici |
| 1-0 | 25 |
2009 |
Reykjavik Open | D91 Grunfeld, 5.Bg5 |
| 18. K Eliasson vs G Halldorsson |
| 1-0 | 38 |
2009 |
Reykjavik Open | B01 Scandinavian |
| 19. G Halldorsson vs G Wagner |
| ½-½ | 20 |
2009 |
European Club Cup | A84 Dutch |
| 20. E Thorsteinsson vs G Halldorsson |
| ½-½ | 7 |
2009 |
Reykjavik Open | A80 Dutch |
| 21. G Halldorsson vs H Thorsteinsdottir |
| ½-½ | 50 |
2009 |
Reykjavik Open | D91 Grunfeld, 5.Bg5 |
| 22. M Alava vs G Halldorsson |
| 1-0 | 32 |
2009 |
European Club Cup | C02 French, Advance |
| 23. G Halldorsson vs J Gunnarsson |
| 0-1 | 60 |
2009 |
Reykjavik Open | A30 English, Symmetrical |
| 24. G Halldorsson vs P Simacek |
| 0-1 | 36 |
2009 |
European Club Cup | A20 English |
| 25. G Halldorsson vs V Sareen |
| 1-0 | 41 |
2010 |
Reykjavik Open | A37 English, Symmetrical |