| Jul 31, 2025 | Kostov | ½–½ | Dolek | Round 5: Kostov, Kiril - Dolek, Gokalp Deniz | Slav Defense: Schlechter Variation | |
| Jul 30, 2025 | Cizer | 0–1 | Kostov | Round 4: Cizer, Ahmet Kaan - Kostov, Kiril | Sicilian Defense: Closed | |
| Jul 29, 2025 | Nochimowski | 0–1 | Kostov | Round 2: Nochimowski, Eran - Kostov, Kiril | Sicilian Defense: Najdorf Variation | |
| Jul 28, 2025 | Kostov | 1–0 | Pastras | Round 1: Kostov, Kiril - Pastras, Ioannis | Ruy Lopez: Closed | |
| Jul 16, 2025 | Kostov | ½–½ | Bai | Round 3: Kostov, Kiril - Bai, Xuhui | Sicilian Defense: French Variation, Westerinen Attack | |
| Aug 4, 2024 | Kostov | 0–1 | Kostov | 13. SPLIT OPEN: ŠAHOVSKI FESTIVAL 2024 | Sicilian Defense: French Variation, Westerinen Attack | |
| Aug 13, 2023 | Kostov | 1–0 | Kostov | 12. Split Open 05.-13.08.2023. | Queen's Pawn Game | |
| Aug 11, 2023 | Saric | 1–0 | Kostov | 12. Split Open 05.-13.08.2023. | Slav Defense: Quiet Variation, Schallopp Defense | |
| Aug 6, 2023 | Kostov | 0–1 | Morgunov | 12. Split Open 05.-13.08.2023. | Sicilian Defense: Richter-Rauzer Variation, Neo-Modern Variation, Nyezhmetdinov Attack | |
| Aug 8, 2021 | Kazakos | * | Kostov | 30th OPEN Chess International Tournament | ? | |
| Aug 7, 2021 | Kostov | * | Kostov | 30th OPEN Chess International Tournament | ? | |
| Aug 6, 2021 | Samaridis | * | Kostov | 30th OPEN Chess International Tournament | ? | |
| Aug 5, 2021 | Kostov | * | Stamoudis | 30th OPEN Chess International Tournament | ? | |
| Aug 4, 2021 | Berbatis | * | Kostov | 30th OPEN Chess International Tournament | ? | |
| Aug 3, 2021 | Kostov | * | Pirvulescu | 30th OPEN Chess International Tournament | ? | |
| Aug 2, 2021 | Kostov | * | Sotiropoulos | 30th OPEN Chess International Tournament | ? | |
| Aug 2, 2021 | Triantafilidis | * | Kostov | 30th OPEN Chess International Tournament | ? | |
| Aug 1, 2021 | Betsakos | * | Kostov | 30th OPEN Chess International Tournament | ? | |
| — | Kostov | 1–0 | Aral | Round 7: Kostov, Kiril - Aral, Demir | Caro-Kann Defense: Tartakower Variation | |
| — | Kostov | ½–½ | Sahin | Round 9: Kostov, Kiril - Sahin, Tuna | Sicilian Defense: Closed | |
| — | Xu | ½–½ | Kostov | Round 6: Xu, Chang(CQ) - Kostov, Kiril | Sicilian Defense: Najdorf Variation | |
| — | Seretis | ½–½ | Kostov | Round 8: Seretis, Nikolaos G - Kostov, Kiril | Sicilian Defense: Najdorf Variation, English Attack | |
