| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 1. H Nielsen vs A Nimzowitsch |
| 0-1 | 35 | 1924 | Simul | B00 Uncommon King's Pawn Opening |
| 2. H Nielsen vs L T Andersen |
| 1-0 | 42 | 1935 | Danish Championship | D85 Grunfeld |
| 3. O Larsen vs H Nielsen |
| 1-0 | 57 | 1935 | Danish Championship | A46 Queen's Pawn Game |
| 4. H Nielsen vs E Sorensen |
| 0-1 | 56 | 1935 | Danish Championship | E30 Nimzo-Indian, Leningrad |
| 5. H Nielsen vs J Gemzoe |
| 1-0 | 39 | 1935 | Danish Championship | D08 Queen's Gambit Declined, Albin Counter Gambit |
| 6. K Poulsen vs H Nielsen |
| ½-½ | 35 | 1935 | Danish Championship | D37 Queen's Gambit Declined |
| 7. P Hage vs H Nielsen |
| ½-½ | 69 | 1935 | Danish Championship | D37 Queen's Gambit Declined |
| 8. H Nielsen vs A Christensen |
| 1-0 | 20 | 1935 | Danish Championship | D13 Queen's Gambit Declined Slav, Exchange Variation |
| 9. C Poulsen vs H Nielsen |
| 1-0 | 53 | 1936 | DEN-ch | D43 Queen's Gambit Declined Semi-Slav |
| 10. H Nielsen vs P Tautvaisas |
| 1-0 | 25 | 1936 | non-FIDE Munich Olympiad | D52 Queen's Gambit Declined |
| 11. O Krassnig vs H Nielsen |
 | 1-0 | 40 | 1936 | non-FIDE Munich Olympiad | C83 Ruy Lopez, Open |
| 12. B Sundberg vs H Nielsen |
| 1-0 | 38 | 1936 | non-FIDE Munich Olympiad | D05 Queen's Pawn Game |
| 13. H Nielsen vs L Colliander |
| 1-0 | 39 | 1936 | non-FIDE Munich Olympiad | A44 Old Benoni Defense |
| 14. B Nielsen vs H Nielsen |
| 1-0 | 21 | 1941 | DEN-ch | C11 French |
| 15. O Larsen vs H Nielsen |
| 0-1 | 25 | 1941 | DEN-ch | A51 Budapest Gambit |
| 16. H Nielsen vs P Korning |
| 1-0 | 36 | 1945 | DEN-ch | D55 Queen's Gambit Declined |
| 17. B Nielsen vs H Nielsen |
| 0-1 | 35 | 1945 | DEN-ch | E34 Nimzo-Indian, Classical, Noa Variation |
| 18. H Nielsen vs B Nielsen |
| 0-1 | 29 | 1946 | DEN-ch | D24 Queen's Gambit Accepted |
| 19. H Nielsen vs E V Nielsen |
| 0-1 | 22 | 1947 | DEN-ch | D43 Queen's Gambit Declined Semi-Slav |
| 20. F Pinzon vs H Nielsen |
| 1-0 | 28 | 1950 | Dubrovnik Olympiad | D37 Queen's Gambit Declined |
| 21. H Nielsen vs H Lambert |
| 0-1 | 37 | 1950 | Dubrovnik Olympiad | E67 King's Indian, Fianchetto |
| 22. Evans vs H Nielsen |
| 1-0 | 36 | 1950 | Dubrovnik Olympiad | D96 Grunfeld, Russian Variation |
| 23. H Nielsen vs J H Donner |
| 0-1 | 37 | 1950 | Dubrovnik Olympiad | C86 Ruy Lopez, Worrall Attack |
| 24. H Nielsen vs H Heikinheimo |
| 1-0 | 43 | 1950 | Dubrovnik Olympiad | D78 Neo-Grunfeld, 6.O-O c6 |
| 25. L Rellstab vs H Nielsen |
| ½-½ | 31 | 1950 | Dubrovnik Olympiad | C17 French, Winawer, Advance |
Kibitzing
