| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 1. B Nielsen vs J Nielsen |
| 0-1 | 27 | 1932 | cr TS90/222 | B18 Caro-Kann, Classical |
| 2. A Nimzowitsch vs J Nielsen |
| 1-0 | 36 | 1933 | Copenhagen Politiken | A28 English |
| 3. J Nielsen vs L Abramavicius |
| 0-1 | 34 | 1933 | Folkestone Olympiad | E67 King's Indian, Fianchetto |
| 4. J Nielsen vs K Berndtsson |
| 0-1 | 58 | 1933 | Folkestone Olympiad | A14 English |
| 5. K Opocensky vs J Nielsen |
 | 1-0 | 43 | 1933 | Folkestone Olympiad | D30 Queen's Gambit Declined |
| 6. J Nielsen vs T Sigurdsson |
| 1-0 | 35 | 1933 | Folkestone Olympiad | A13 English |
| 7. R Combe vs J Nielsen |
| ½-½ | 30 | 1933 | Folkestone Olympiad | D68 Queen's Gambit Declined, Orthodox Defense, Classical |
| 8. J Nielsen vs Duchamp |
| 1-0 | 70 | 1933 | Folkestone Olympiad | A04 Reti Opening |
| 9. I Appel vs J Nielsen |
| 1-0 | 37 | 1933 | Folkestone Olympiad | D67 Queen's Gambit Declined, Orthodox Defense, Bd3 line |
| 10. J Nielsen vs F Igel |
| 0-1 | 31 | 1933 | Folkestone Olympiad | A13 English |
| 11. J Nielsen vs E Andersen |
| 0-1 | 22 | 1934 | DEN-ch | A46 Queen's Pawn Game |
| 12. J Nielsen vs J Enevoldsen |
| 0-1 | 30 | 1934 | Nordic Congress, Copenhagen | D67 Queen's Gambit Declined, Orthodox Defense, Bd3 line |
| 13. J Nielsen vs J Gemzoe |
| ½-½ | 39 | 1934 | Nordic Congress, Copenhagen | D63 Queen's Gambit Declined, Orthodox Defense |
| 14. P Hage vs J Nielsen |
| 0-1 | 21 | 1934 | Nordic Congress, Copenhagen | D08 Queen's Gambit Declined, Albin Counter Gambit |
| 15. N Lie vs J Nielsen |
| 1-0 | 28 | 1934 | Nordic Congress, Copenhagen | D02 Queen's Pawn Game |
| 16. J Nielsen vs B Nielsen |
| ½-½ | 48 | 1934 | Nordic Congress, Copenhagen | D63 Queen's Gambit Declined, Orthodox Defense |
| 17. Harald Hallas vs J Nielsen |
| 0-1 | 21 | 1934 | Nordic Congress, Copenhagen | A09 Reti Opening |
| 18. J Nielsen vs O Kinnmark |
| ½-½ | 38 | 1934 | Nordic Congress, Copenhagen | E71 King's Indian, Makagonov System (5.h3) |
| 19. H C Christoffersen vs J Nielsen |
| 0-1 | 26 | 1934 | Nordic Congress, Copenhagen | B13 Caro-Kann, Exchange |
| 20. Keres vs J Nielsen |
| 0-1 | 52 | 1935 | corr | C46 Three Knights |
| 21. N Lie vs J Nielsen |
| ½-½ | 30 | 1935 | Danish Championship | D02 Queen's Pawn Game |
| 22. J Nielsen vs O Larsen |
| 1-0 | 53 | 1935 | Danish Championship | D52 Queen's Gambit Declined |
| 23. A Desler vs J Nielsen |
| 0-1 | 52 | 1935 | Danish Championship | C63 Ruy Lopez, Schliemann Defense |
| 24. J Nielsen vs A Christensen |
| 1-0 | 47 | 1935 | Danish Championship | D18 Queen's Gambit Declined Slav, Dutch |
| 25. E Sorensen vs J Nielsen |
| ½-½ | 49 | 1935 | Danish Championship | C63 Ruy Lopez, Schliemann Defense |
Kibitzing
