| Jun 20, 2026 | Kostolansky | ½–½ | Bochnicka | Majstrovstva SR | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Jun 19, 2026 | Sahidi | 1–0 | Kostolansky | Majstrovstva SR | Queen's Gambit Declined | |
| Jun 19, 2026 | Kostolansky | ½–½ | Michalik | Majstrovstva SR | Caro-Kann Defense: Advance Variation, Tal Variation | |
| Jun 17, 2026 | Neugebauer | 0–1 | Kostolansky | Majstrovstva SR | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Jun 17, 2026 | Kostolansky | ½–½ | Haring | Majstrovstva SR | Sicilian Defense: Moscow Variation | |
| Jun 16, 2026 | Gazik | 1–0 | Kostolansky | Majstrovstva SR | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Jun 14, 2026 | Kostolansky | ½–½ | Rybka | Majstrovstva SR | Sicilian Defense: Moscow Variation, Main Line | |
| Jun 13, 2026 | Ftacnik | ½–½ | Kostolansky | Majstrovstva SR | Semi-Slav Defense | |
| Jun 13, 2026 | Kostolansky | ½–½ | Druska | Majstrovstva SR | Zukertort Opening | |
| May 2, 2026 | Liang | 1–0 | Kostolansky | rated rapid game | Zukertort Opening | |
| May 2, 2026 | Varela Velazquez | 0–1 | Kostolansky | rated rapid game | Sicilian Defense: Taimanov Variation, Bastrikov Variation | |
| May 2, 2026 | Kostolansky | 1–0 | Oosthuizen | rated rapid game | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| May 2, 2026 | Chacon Salinas | 1–0 | Kostolansky | rated rapid game | Catalan Opening: Closed | |
| May 2, 2026 | Kostolansky | 1–0 | Veliz | rated rapid game | Zukertort Opening | |
| May 2, 2026 | Aryan Chopra | 1–0 | Kostolansky | rated rapid game | King's Indian Attack | |
| May 2, 2026 | Kostolansky | 1–0 | Mihir Godawat | rated rapid game | King's Indian Defense: Orthodox Variation, Positional Defense, Main Line | |
| Jan 19, 2026 | Cherukuri | 0–1 | Kostolansky | Round 9: Cherukuri, Nitesh - Kostolansky, Sebastian Lukas | Sicilian Defense: Taimanov Variation | |
| Jan 19, 2026 | Kostolansky | 1–0 | Adam | Round 8: Kostolansky, Sebastian Lukas - Adam, Rafael | Ruy Lopez: Closed, Anti-Marshall | |
| Jan 18, 2026 | Peycheva | ½–½ | Kostolansky | Round 7: Peycheva, Gergana - Kostolansky, Sebastian Lukas | Catalan Opening: Closed | |
| Jan 18, 2026 | Kostolansky | 1–0 | Paragua | Round 6: Kostolansky, Sebastian Lukas - Paragua, Megan Althea | English Opening: Anglo-Indian Defense, King's Knight Variation | |
| Jan 17, 2026 | Bortnyk | ½–½ | Kostolansky | Round 5: Bortnyk, Mykola - Kostolansky, Sebastian Lukas | Semi-Slav Defense | |
| Jan 17, 2026 | Kostolansky | 1–0 | Hoffman | Round 4: Kostolansky, Sebastian Lukas - Hoffman, Luc | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Jan 16, 2026 | Xu | 1–0 | Kostolansky | Round 3: Xu, Grant - Kostolansky, Sebastian Lukas | Rapport-Jobava System | |
| Jan 16, 2026 | Kostolansky | 1–0 | Ho | Round 2: Kostolansky, Sebastian Lukas - Ho, Carter | Sicilian Defense: French Variation, Westerinen Attack | |
| Jan 14, 2026 | Kostolansky | ½–½ | Stremavicius | Round 1: Kostolansky, Sebastian Lukas - Stremavicius, Pijus | Caro-Kann Defense: Panov Attack | |
| Jan 5, 2026 | Paramzina | 0–1 | Kostolansky | Round 6: Paramzina, Anastasya - Kostolansky, Sebastian Lukas | Sicilian Defense: Delayed Alapin Variation, with e6 | |
| Jan 4, 2026 | Kostolansky | 1–0 | Boyer | Round 5: Kostolansky, Sebastian Lukas - Boyer, Mahel | French Defense: Steinitz Variation, Boleslavsky Variation | |
| Jan 3, 2026 | Cardoso Cardoso | 1–0 | Kostolansky | Round 3: Cardoso Cardoso, Jose Gabriel - Kostolansky, Sebastian Lukas | Sicilian Defense: Taimanov Variation | |
| Feb 2, 2025 | Kostolansky | 0–1 | Shlyakhtenko | Rated rapid game | Sicilian Defense: French Variation, Westerinen Attack | |
| Feb 2, 2025 | Biletskyy | 0–1 | Kostolansky | Rated rapid game | Sicilian Defense: Smith-Morra Gambit | |
| Feb 1, 2025 | Kostolansky | 1–0 | Ghimpu | Rated rapid game | French Defense: MacCutcheon Variation, Dr. Olland Variation | |
| Feb 1, 2025 | Kostolansky | 1–0 | Wang | Rated rapid game | Caro-Kann Defense: Advance Variation, Tal Variation | |
| Jan 5, 2025 | Kostolansky | 0–1 | Caglar | Round 6: Kostolansky, Sebastian Lukas - Caglar, Sila | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Jan 4, 2025 | Kostolansky | ½–½ | Rodrigue-Lemieux | Round 4: Kostolansky, Sebastian Lukas - Rodrigue-Lemieux, Shawn | Ruy Lopez: Morphy Defense, Norwegian Variation | |
| Jan 4, 2025 | Daggupati | 1–0 | Kostolansky | Round 5: Daggupati, Balaji - Kostolansky, Sebastian Lukas | Sicilian Defense: Taimanov Variation, Bastrikov Variation | |
| Jan 3, 2025 | Kostolansky | 1–0 | Zhang | Round 2: Kostolansky, Sebastian Lukas - Zhang, Henry | Sicilian Defense: Moscow Variation | |
| Jan 3, 2025 | Budisavljevic | ½–½ | Kostolansky | Round 3: Budisavljevic, Luka - Kostolansky, Sebastian Lukas | Nimzo-Indian Defense: Kmoch Variation | |
| Dec 30, 2024 | Kostolansky | 0–1 | Andersen | FIDE World Blitz Chess Championship 2024 | Ruy Lopez: Closed, Anti-Marshall | |
| Dec 30, 2024 | Kostolansky | 0–1 | Soo | FIDE World Blitz Chess Championship 2024 | French Defense: Winawer Variation, Portisch-Hook Variation | |
| Dec 30, 2024 | Kostolansky | 0–1 | Meylan | FIDE World Blitz Chess Championship 2024 | French Defense: Alekhine-Chatard Attack, Maróczy Variation | |
| Dec 30, 2024 | Kostolansky | 1–0 | Wanyama | FIDE World Blitz Chess Championship 2024 | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Dec 30, 2024 | Kostolansky | ½–½ | Bezold | FIDE World Blitz Chess Championship 2024 | Sicilian Defense: Kan Variation, Maróczy Bind, Réti Variation | |
| Dec 30, 2024 | Kostolansky | 0–1 | Nesterov | FIDE World Blitz Chess Championship 2024 | Petrov's Defense: Modern Attack, Center Variation | |
| Dec 30, 2024 | Hakobyan | 1–0 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Queen's Gambit Declined: Barmen Variation | |
| Dec 30, 2024 | Safarli | 1–0 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Sicilian Defense: French Variation | |
| Dec 30, 2024 | Ahmed | 0–1 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Sicilian Defense: Closed, Fianchetto Variation | |
| Dec 30, 2024 | Banh Gia Huy | 1–0 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Queen's Pawn Game: London System | |
| Dec 30, 2024 | Pereira | 0–1 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Dec 30, 2024 | Gaehwiler | 0–1 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Catalan Opening: Closed | |
| Dec 30, 2024 | Chirila | 1–0 | Kostolansky | FIDE World Blitz Chess Championship 2024 | Queen's Gambit Declined: Barmen Variation | |
| Sep 21, 2024 | Kostolansky | ½–½ | Laurusas | 45th FIDE Chess Olympiad | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Sep 20, 2024 | Fitzsimons | 0–1 | Kostolansky | 45th FIDE Chess Olympiad | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Sep 19, 2024 | Kojima | 0–1 | Kostolansky | 45th FIDE Chess Olympiad | Queen's Gambit Declined: Exchange Variation, Sämisch Variation | |
| Sep 18, 2024 | Kostolansky | ½–½ | Zia | 45th FIDE Chess Olympiad | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Sep 16, 2024 | Kelires | 1–0 | Kostolansky | 45th FIDE Chess Olympiad | Catalan Opening: Closed | |
| Sep 15, 2024 | Gengler | 0–1 | Kostolansky | 45th FIDE Chess Olympiad | Sicilian Defense: Kan Variation | |
| Sep 13, 2024 | Kostolansky | 1–0 | Sanal | 45th FIDE Chess Olympiad | Ruy Lopez: Berlin Defense | |
| Sep 12, 2024 | Mariano | 0–1 | Kostolansky | 45th FIDE Chess Olympiad | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Sep 11, 2024 | Kostolansky | ½–½ | Al Busaidi | 45th FIDE Chess Olympiad | Caro-Kann Defense: Advance Variation, Tal Variation | |
| Jun 22, 2024 | Kostolansky | ½–½ | Neugebauer | MSR 2024 | Sicilian Defense: Moscow Variation, Main Line | |
| Jun 21, 2024 | Ftacnik | ½–½ | Kostolansky | MSR 2024 | English Opening: Anglo-Indian Defense, King's Knight Variation | |
| Jun 20, 2024 | Kostolansky | ½–½ | Bochnicka | MSR 2024 | Ruy Lopez: Morphy Defense, Classical Defense Deferred | |
| Jun 20, 2024 | Ftacnik | * | Kostolansky | MSR 2024 | ? | |
| Jun 19, 2024 | Borosova | ½–½ | Kostolansky | MSR 2024 | Indian Defense: London System | |
| Jun 18, 2024 | Kostolansky | 0–1 | Sahidi | MSR 2024 | Sicilian Defense: Moscow Variation | |
| Jun 17, 2024 | Jurcik | ½–½ | Kostolansky | MSR 2024 | Sicilian Defense: French Variation, Westerinen Attack | |
| Jun 16, 2024 | Kostolansky | 0–1 | Haring | MSR 2024 | Ruy Lopez: Closed, Breyer Defense, Zaitsev Hybrid | |
| Jun 15, 2024 | Druska | 0–1 | Kostolansky | MSR 2024 | Sicilian Defense: French Variation, Open | |
| Jun 14, 2024 | Gazik | ½–½ | Kostolansky | MSR 2024 | Sicilian Defense: French Variation, Westerinen Attack | |
| Jan 21, 2024 | Pechac | ½–½ | Kostolansky | extraliga2324 | Sicilian Defense: Four Knights Variation, Cobra Variation | |
| Jul 17, 2024 | Kostolansky | 0–1 | Mohamed Anees M | Slovakia chess Open PN 24 | Sicilian Defense: Pin Variation, Koch Variation | |
| Jul 16, 2024 | Rybka | ½–½ | Kostolansky | Slovakia chess Open PN 24 | Sicilian Defense: French Variation, Westerinen Attack | |
| Jul 15, 2024 | Kostolansky | 0–1 | Stremavicius | Slovakia chess Open PN 24 | Caro-Kann Defense: Advance Variation, Tal Variation | |
| Jul 14, 2024 | Delgerdalai | 0–1 | Kostolansky | Slovakia chess Open PN 24 | Sicilian Defense: Taimanov Variation, Bastrikov Variation | |
| Jul 13, 2024 | Kostolansky | ½–½ | Balint | Slovakia chess Open PN 24 | Ruy Lopez: Closed, Anti-Marshall | |
| Jul 12, 2024 | Demchenko | 1–0 | Kostolansky | Slovakia chess Open PN 24 | Sicilian Defense: French Variation | |
| Jul 11, 2024 | Kostolansky | 1–0 | Rakshitta Ravi | Slovakia chess Open PN 24 | Ruy Lopez: Morphy Defense, Neo-Arkhangelsk Variation | |
| Jul 10, 2024 | Marakovits | 0–1 | Kostolansky | Slovakia chess Open PN 24 | Queen's Gambit Declined: Three Knights Variation | |
| Jul 9, 2024 | Kostolansky | ½–½ | Ajay Santhosh Parvathareddy | Slovakia chess Open PN 24 | Sicilian Defense: Delayed Alapin Variation, with d6 | |
| May 4, 2024 | Kostolansky | ½–½ | Haring | Extraliga 20224 | Ruy Lopez: Morphy Defense | |
| May 3, 2024 | Kostolansky | ½–½ | Nemeth | Extraliga 2023/24 | Ruy Lopez: Closed | |
| Feb 25, 2024 | Kostolansky | ½–½ | Saric | Extraliga 8.kolo | Sicilian Defense: Moscow Variation | |
| Dec 10, 2023 | Kraus | ½–½ | Kostolansky | SVK ECo-C Extraliga 2023/2024 | Queen's Pawn Game: Colle System | |
| Dec 9, 2023 | Kostolansky | ½–½ | Jakab | SVK ECo-C Extraliga 2023/2024 | French Defense: Winawer Variation, Advance Variation | |
| Nov 24, 2023 | Pozzari | ½–½ | Kostolansky | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Catalan Opening: Closed | |
| Nov 23, 2023 | Kostolansky | ½–½ | Jiang | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Nov 22, 2023 | Unneland | ½–½ | Kostolansky | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Nov 21, 2023 | Kostolansky | 1–0 | Nied | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Ruy Lopez: Berlin Defense | |
| Nov 20, 2023 | Loftgaard | 1–0 | Kostolansky | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Delayed Alapin Variation, with e6 | |
| Nov 18, 2023 | Kostolansky | ½–½ | Liu | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack, Fianchetto Variation | |
| Nov 17, 2023 | Juhasz | 1–0 | Kostolansky | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Taimanov Variation, Bastrikov Variation, English Attack | |
| Nov 16, 2023 | Kostolansky | ½–½ | Wong | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Delayed Alapin Variation | |
| Nov 15, 2023 | Marakovits | 0–1 | Kostolansky | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Nimzo-Indian Defense: Normal Variation, Bernstein Defense | |
| Nov 14, 2023 | Kostolansky | ½–½ | Kristoferitsch | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Sicilian Defense: Moscow Variation, Main Line | |
| Nov 13, 2023 | Pegno | 0–1 | Kostolansky | FIDEWORLDYOUTHCHESSCHAMPIONSHIP Open 18 | Nimzo-Indian Defense: Classical Variation, Noa Variation | |
| Nov 5, 2023 | Kostolansky | 1–0 | Turcan | SVK ECo-C Extraliga 2023/2024 | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Nov 4, 2023 | Sahidi | ½–½ | Kostolansky | SVK ECo-C Extraliga 2023/2024 | Semi-Slav Defense: Stoltz Variation | |
| Jul 9, 2023 | Kostolansky | 1–0 | Haring | Slovak Championship | GM | Sicilian Defense: Kan Variation, Maróczy Bind, Réti Variation | |
| Jul 8, 2023 | Mazur | ½–½ | Kostolansky | Slovak Championship | GM | Sicilian Defense: Taimanov Variation | |
| Jul 7, 2023 | Kostolansky | 0–1 | Druska | Slovak Championship | GM | Caro-Kann Defense: Advance Variation, Tal Variation | |