| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 1. O Nilsson vs F Bengtsson |
| ½-½ | 65 | 1916 | Nordic Congress-B 7th | C45 Scotch Game |
| 2. K Berndtsson vs O Nilsson |
| ½-½ | 67 | 1916 | Nordic Congress-B 7th | C01 French, Exchange |
| 3. O Nilsson vs B Owesson |
 | ½-½ | 60 | 1916 | Nordic Congress-B 7th | B43 Sicilian, Kan, 5.Nc3 |
| 4. B Rask vs O Nilsson |
| 0-1 | 54 | 1916 | Nordic Congress-B 7th | D40 Queen's Gambit Declined, Semi-Tarrasch |
| 5. O Nilsson vs S Krenzisky |
| 1-0 | 30 | 1919 | Nordic Congress, Gothenburg | C01 French, Exchange |
| 6. A Hakansson vs O Nilsson |
| ½-½ | 30 | 1919 | Nordic Congress, Gothenburg | D40 Queen's Gambit Declined, Semi-Tarrasch |
| 7. O Nilsson vs A Larsson |
| ½-½ | 40 | 1919 | Nordic Congress, Gothenburg | C78 Ruy Lopez |
| 8. A Olson vs O Nilsson |
| 1-0 | 17 | 1919 | Nordic Congress, Gothenburg | C29 Vienna Gambit |
| 9. O Nilsson vs G Nyholm |
| 0-1 | 59 | 1919 | Nordic Congress, Gothenburg | C45 Scotch Game |
| 10. O Nilsson vs J Ryden |
| ½-½ | 63 | 1919 | Nordic Congress, Gothenburg | C47 Four Knights |
| 11. V Sjoberg vs O Nilsson |
| 1-0 | 35 | 1919 | Nordic Congress, Gothenburg | D63 Queen's Gambit Declined, Orthodox Defense |
| 12. O Nilsson vs C Haralds |
| ½-½ | 30 | 1919 | Nordic Congress, Gothenburg | C47 Four Knights |
| 13. A Ahlberg vs O Nilsson |
| 0-1 | 28 | 1919 | Nordic Congress, Gothenburg | C77 Ruy Lopez |
| 14. O Nilsson vs Spielmann |
| ½-½ | 46 | 1919 | Nordic Congress, Gothenburg | C47 Four Knights |
| 15. O Lowenborg vs O Nilsson |
| 0-1 | 50 | 1919 | Nordic Congress, Gothenburg | C82 Ruy Lopez, Open |
| 16. O Nilsson vs H Norman-Hansen |
| ½-½ | 55 | 1920 | Gothenburg C | B01 Scandinavian |
| 17. H Wium vs O Nilsson |
| ½-½ | 37 | 1920 | Gothenburg C | B21 Sicilian, 2.f4 and 2.d4 |
| 18. O Nilsson vs G J Gustafson |
| 1-0 | 37 | 1920 | Gothenburg C | C47 Four Knights |
| 19. O Nilsson vs A M Erichsen |
| ½-½ | 34 | 1920 | Gothenburg C | C83 Ruy Lopez, Open |
| 20. J A Brekke vs O Nilsson |
| ½-½ | 24 | 1920 | Gothenburg C | D05 Queen's Pawn Game |
| 21. O Nilsson vs A Kier |
| 1-0 | 54 | 1920 | Gothenburg C | C45 Scotch Game |
| 22. K Beskow vs O Nilsson |
 | 0-1 | 47 | 1920 | Gothenburg C | C77 Ruy Lopez |
| 23. O Nilsson vs T C Jensen |
| 1-0 | 26 | 1920 | Gothenburg C | B58 Sicilian |
| 24. B Eriksson vs O Nilsson |
| 0-1 | 63 | 1920 | Gothenburg C | D45 Queen's Gambit Declined Semi-Slav |
| 25. O Nilsson vs R Svanberg |
| 1-0 | 37 | 1920 | Gothenburg C | C01 French, Exchange |
Kibitzing
