| Apr 10, 2026 | Panasiuk | 1–0 | Nikolaidis | EICC 2026 | English Opening | |
| Apr 9, 2026 | Nikolaidis | 0–1 | Ilko-Toth | EIIC 2026 | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Apr 8, 2026 | Piddubna | ½–½ | Nikolaidis | EIIC 2026 | English Opening: Anglo-Indian Defense, Slav Formation | |
| Apr 7, 2026 | Nikolaidis | 0–1 | Isik | EIIC 2026 | Queen's Gambit Declined: Exchange Variation, Positional Variation | |
| Oct 31, 2025 | Wegemund | ½–½ | Nikolaidis | Round 10: Wegemund, Hubert - Nikolaidis, Konstantinos | Sicilian Defense: Moscow Variation | |
| Oct 30, 2025 | Nikolaidis | ½–½ | Ray | Round 9: Nikolaidis, Konstantinos - Ray, Sarathi | Semi-Slav Defense: Quiet Variation | |
| Oct 29, 2025 | Zielinski | ½–½ | Nikolaidis | Round 8: Zielinski, Olgierd - Nikolaidis, Konstantinos | French Defense: Steiner Variation | |
| Oct 28, 2025 | Nikolaidis | ½–½ | Kindt | Round 7: Nikolaidis, Konstantinos - Kindt, Manfred | Grünfeld Defense: Three Knights Variation, Petrosian System | |
| Oct 26, 2025 | Tunge | ½–½ | Nikolaidis | Round 6: Tunge, Christian - Nikolaidis, Konstantinos | English Opening: Agincourt Defense, Neo-Catalan Declined | |
| Oct 25, 2025 | Nikolaidis | ½–½ | Mauron | Round 5: Nikolaidis, Konstantinos - Mauron, Pierre | Queen's Gambit Declined: Exchange Variation, Positional Variation | |
| Oct 24, 2025 | Sudharsan | ½–½ | Nikolaidis | Round 4: Sudharsan, Krishnan - Nikolaidis, Konstantinos | Queen's Indian Defense: Miles Variation | |
| Oct 23, 2025 | Chabanon | 1–0 | Nikolaidis | Round 3: Chabanon, Jean-Luc - Nikolaidis, Konstantinos | Queen's Gambit Declined: Ragozin Defense, Alekhine Variation | |
| Oct 22, 2025 | Nikolaidis | ½–½ | Lacasa Diaz | Round 2: Nikolaidis, Konstantinos - Lacasa Diaz, Josep Anton | Sicilian Defense: Dragon Variation | |
| Oct 21, 2025 | Nikolaidis | 1–0 | Pammer | Round 1: Nikolaidis, Konstantinos - Pammer, Florence | King's Pawn Game | |
| Oct 2, 2025 | Nikolaidis | 0–1 | Kniest | European individual senior chess championship 2025 - Open 50+, Rabac, Croatia | Queen's Gambit Declined: Exchange Variation, Positional Variation | |
| Oct 1, 2025 | Stets | ½–½ | Nikolaidis | European individual senior chess championship 2025 - Open 50+, Rabac, Croatia | Indian Defense: Knights Variation | |
| Sep 30, 2025 | Nikolaidis | ½–½ | Mrva | European individual senior chess championship 2025 - Open 50+, Rabac, Croatia | King's Indian Defense: Averbakh Variation, Nc6 Defense | |
| Sep 28, 2025 | Nikolaidis | 0–1 | Fercec | European individual senior chess championship 2025 - Open 50+, Rabac, Croatia | Modern Defense: Standard Defense | |
| Jul 28, 2025 | Eren | 1–0 | Nikolaidis | Round 1: Eren, Ataberk - Nikolaidis, Konstantinos | Sicilian Defense: Najdorf Variation, Adams Attack | |
| Jun 16, 2025 | Nikolaidis | 0–1 | Alexiadis | Round 3: Nikolaidis, Konstantinos - Alexiadis, Hristos | ? | |
| Jun 15, 2025 | Voutsas | 0–1 | Nikolaidis | Round 2: Voutsas, Leonidas - Nikolaidis, Konstantinos | Sicilian Defense: Najdorf Variation | |
| Jun 14, 2025 | Nikolaidis | 1–0 | Veskoukis | Round 1: Nikolaidis, Konstantinos - Veskoukis, Konstantinos | Nimzo-Indian Defense: Normal Variation, Classical Defense | |
| Mar 15, 2025 | Nikolaidis | 0–1 | Horvath | Round 1: Nikolaidis, Konstantinos - Horvath, Dominik | Sicilian Defense: Four Knights Variation, Cobra Variation | |
| Nov 2, 2024 | Lacasa Diaz | ½–½ | Nikolaidis | Round 9: Lacasa Diaz, Josep Anton - Nikolaidis, Konstantinos | English Opening: Anglo-Indian Defense, Nimzo-English | |
| Nov 1, 2024 | Nikolaidis | ½–½ | Cmiel | Round 8: Nikolaidis, Konstantinos - Cmiel, Thorsten | French Defense: Steinitz Variation, Boleslavsky Variation | |
| Oct 31, 2024 | Nikolaidis | 1–0 | Rewitz | Round 7: Nikolaidis, Konstantinos - Rewitz, Poul | Caro-Kann Defense: Advance Variation, Short Variation | |
| Oct 30, 2024 | Sielecki | ½–½ | Nikolaidis | Round 6: Sielecki, Christof - Nikolaidis, Konstantinos | Sicilian Defense: Moscow Variation | |
| Oct 29, 2024 | Nikolaidis | 1–0 | Naslund | Round 5: Nikolaidis, Konstantinos - Naslund, Mikael | Scandinavian Defense: Gubinsky-Melts Defense | |
| Oct 28, 2024 | Mrva | 1–0 | Nikolaidis | Round 4: Mrva, Martin - Nikolaidis, Konstantinos | Sicilian Defense: Najdorf Variation | |
| Oct 27, 2024 | Nikolaidis | 1–0 | Cardili | Round 3: Nikolaidis, Konstantinos - Cardili, Mariano | Caro-Kann Defense: Advance Variation, Tal Variation | |
| Jul 10, 2024 | Nikolaidis | ½–½ | Papasimakopoulos | Greek League 2024 | Queen's Indian Defense: Fianchetto Variation, Check Variation, Intermezzo Line | |
| Jul 8, 2024 | Nikolaidis | ½–½ | Mitsis | Greek League 2024 | Queen's Gambit Declined: Three Knights, Vienna Variation | |
| Jul 7, 2024 | Nikolaidis | 0–1 | Bozinakis | Greek League 2024 | Mexican Defense | |
| Jul 6, 2024 | Nikolaidis | ½–½ | Banikas | Greek League 2024 | Tarrasch Defense: Symmetrical Variation | |
| Jul 5, 2024 | Papadimitriou | 1–0 | Nikolaidis | Greek League 2024 | King's Indian Attack: Yugoslav Variation | |
| Jul 5, 2024 | Nikolaidis | ½–½ | Nasos | Greek League 2024 | Queen's Gambit Declined: Charousek Variation | |
| Aug 10, 2024 | Nikolaidis | 0–1 | Stratigos | Round 6: Nikolaidis, Konstantinos - Stratigos, Spiros | King's Indian Defense: Makogonov Variation | |
| Aug 9, 2024 | Mastrovasilis | 1–0 | Nikolaidis | Round 5: Mastrovasilis, Athanasios - Nikolaidis, Konstantinos | Nimzo-Indian Defense: Normal Variation | |
| Aug 8, 2024 | Karamichos | 0–1 | Nikolaidis | Round 4: Karamichos, Michail - Nikolaidis, Konstantinos | Sicilian Defense: Moscow Variation | |
| Aug 7, 2024 | Nikolaidis | ½–½ | Pelantakis | Round 3: Nikolaidis, Konstantinos - Pelantakis, Mihail | Latvian Gambit: Clam Gambit | |
| Oct 30, 2023 | Konstantinos Nikolaidis | ½–½ | Renzo Mantovani | 50+ World Senior Championship | English Opening: Symmetrical, Hedgehog, Flexible Formation | |
| Oct 29, 2023 | Cummings | ½–½ | Nikolaidis | 50+ World Senior Championship | English Opening: Anglo-Indian Defense, King's Knight Variation | |
| Oct 28, 2023 | Nikolaidis | ½–½ | Plotkin | 50+ World Senior Championship | English Opening: Symmetrical Variation, Four Knights Variation | |
| Oct 27, 2023 | Lima | 1–0 | Nikolaidis | 50+ World Senior Championship | English Opening: Anglo-Indian Defense | |
| Oct 26, 2023 | Nikolaidis | * | Holzke | 50+ World Senior Championship | ? | |
| Oct 25, 2023 | Degraeve | 0–1 | Nikolaidis | 50+ World Senior Championship | Sicilian Defense: Modern Variations | |
| Jun 17, 2023 | KONSTANTINOS NIKOLAIDIS | 1–0 | STYLIANOS BANAS | Round 1: KONSTANTINOS NIKOLAIDIS - STYLIANOS BANAS | Queen's Gambit Declined: Exchange Variation, Positional Variation | |