| May 24, 2026 | Posthuma | ½–½ | Sam | 35th Annual Chicago Open | Catalan Opening | |
| May 23, 2026 | Jacobson | 1–0 | Posthuma | Round 5: Jacobson, Brandon - Posthuma, Joshua | Queen's Gambit Declined: Exchange Variation, Positional Variation | |
| May 23, 2026 | Posthuma | ½–½ | Sonis | Round 4: Posthuma, Joshua - Sonis, Francesco | Catalan Opening | |
| Nov 30, 2025 | Posthuma | ½–½ | Budisavljevic | Round 8: Posthuma, Joshua - Budisavljevic, Luka | Horwitz Defense | |
| Nov 28, 2025 | Parkhov | 1–0 | Posthuma | Round 4: Parkhov, Yair - Posthuma, Joshua | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Jul 10, 2025 | Putnam | ½–½ | Posthuma | Round 1: Putnam, Liam - Posthuma, Joshua | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Jul 7, 2025 | Matviishen | ½–½ | Posthuma | Round 9: Matviishen, Viktor - Posthuma, Joshua | Caro-Kann Defense: Exchange Variation | |
| Jul 7, 2025 | Posthuma | 1–0 | Zeltsan | Round 8: Posthuma, Joshua - Zeltsan, Joseph | Rapport-Jobava System | |
| Jul 7, 2025 | Griffith | 1–0 | Posthuma | Round 7: Griffith, Kyron - Posthuma, Joshua | Sicilian Defense: Hyperaccelerated Fianchetto | |
| Jul 7, 2025 | Posthuma | 0–1 | Narayanan | Round 6: Posthuma, Joshua - Narayanan, Samrug | Catalan Opening: Closed | |
| Jul 7, 2025 | Tian | ½–½ | Posthuma | Round 5: Tian, Eddy - Posthuma, Joshua | Catalan Opening: Closed | |
| Jul 7, 2025 | Posthuma | 1–0 | Cordova | Round 4: Posthuma, Joshua - Cordova, Emilio | Catalan Opening | |
| Jul 7, 2025 | Torres Rosas | 0–1 | Posthuma | Round 3: Torres Rosas, Luis Carlos - Posthuma, Joshua | Queen's Gambit Declined: Exchange Variation, Positional Variation | |
| Jul 7, 2025 | Posthuma | 0–1 | Kevlishvili | Round 2: Posthuma, Joshua - Kevlishvili, Robby | Sicilian Defense: Modern Variations | |
| Jul 6, 2025 | Posthuma | * | Li | 53rd Annual World Open Chess Tournament | ? | |
| Jul 5, 2025 | Wu | * | Posthuma | 53rd Annual World Open Chess Tournament | ? | |
| Jul 4, 2025 | Posthuma | 0–1 | Kevlishvili | 53rd Annual World Open Chess Tournament | ? | |
| Aug 20, 2024 | Pap | ½–½ | Posthuma | Budapest One Week GMA | Caro-Kann Defense: Two Knights Attack | |
| Aug 19, 2024 | Posthuma | 1–0 | Grover | Budapest One Week GMA | Catalan Opening | |
| Aug 18, 2024 | Posthuma | 1–0 | Chubakov | Budapest One Week GMA | Queen's Pawn Game: Accelerated London System, Steinitz Countergambit | |
| Aug 18, 2024 | Tyurin | ½–½ | Posthuma | Budapest One Week GMA | King's Indian Defense: Normal Variation, Rare Defenses | |
| Aug 17, 2024 | Setyaki | ½–½ | Posthuma | Budapest One Week GMA | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Aug 16, 2024 | Posthuma | 0–1 | Damjanovic | Budapest One Week GMA | Lion Defense: Lion's Jaw | |
| Aug 16, 2024 | Gombocz | ½–½ | Posthuma | Budapest One Week GMA | English Opening | |
| Aug 15, 2024 | Posthuma | * | Nguyen | Budapest One Week GMA | Queen's Pawn Game: Accelerated London System, Steinitz Countergambit | |
| Aug 14, 2024 | Fus | ½–½ | Posthuma | Budapest One Week GMA | English Opening: Anglo-Indian Defense, Queen's Knight Variation | |
| Jun 30, 2024 | Corrales Jimenez | 1–0 | Posthuma | Round 7: Corrales Jimenez, Fidel - Posthuma, Joshua | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Mar 31, 2024 | Posthuma | ½–½ | Melillo | Round 9: Posthuma, Joshua - Melillo, Lucius | Zukertort Opening: Sicilian Invitation | |
| Mar 31, 2024 | Wu | 0–1 | Posthuma | Round 8: Wu, Sibo - Posthuma, Joshua | Queen's Pawn Game: Modern Defense | |
| Mar 30, 2024 | Posthuma | 1–0 | Nguyen | Round 7: Posthuma, Joshua - Nguyen, James Le | Queen's Pawn Game: Accelerated London System, Steinitz Countergambit | |
| Mar 30, 2024 | Kunka | ½–½ | Posthuma | Round 6: Kunka, Harshid - Posthuma, Joshua | Sicilian Defense: O'Kelly Variation, Venice System | |
| Mar 29, 2024 | Posthuma | 1–0 | Horobetz | Round 5: Posthuma, Joshua - Horobetz, Graham | Indian Defense | |
| Mar 29, 2024 | Mendez Tovar | 0–1 | Posthuma | Round 4: Mendez Tovar, Yessica Yissel - Posthuma, Joshua | Sicilian Defense: Accelerated Dragon, Modern Bc4 Variation | |
| Mar 28, 2024 | Posthuma | 1–0 | Fierro Baquero | Round 3: Posthuma, Joshua - Fierro Baquero, Martha L. | Pterodactyl Defense: Eastern, Pterodactyl | |
| Mar 28, 2024 | Eckert | ½–½ | Posthuma | Round 2: Eckert, Doug - Posthuma, Joshua | English Opening: Agincourt Defense, Neo-Catalan Declined | |
| Mar 27, 2024 | Komarov | ½–½ | Posthuma | Round 1: Komarov, Dimitri - Posthuma, Joshua | King's Indian Defense: Normal Variation, Rare Defenses | |
| Jun 29, 2024 | Singh | * | Posthuma | 17th Annual Philadelphia International | ? | |
| Jun 27, 2024 | Posthuma | * | Sriniaiyer | 17th Annual Philadelphia International | ? | |
| May 24, 2022 | Grabinsky | ½–½ | Posthuma | 2022 Saint Louis Norm Congress - International Master | Caro-Kann Defense: Two Knights Attack | |
| May 23, 2022 | Posthuma | 1–0 | Antova | 2022 Saint Louis Norm Congress - International Master | Semi-Slav Defense: Quiet Variation | |
| May 22, 2022 | Posthuma | 1–0 | Paul Chambers | 2022 Saint Louis Norm Congress - International Master | Semi-Slav Defense: Quiet Variation | |
| May 22, 2022 | Marek | ½–½ | Posthuma | 2022 Saint Louis Norm Congress - International Master | Caro-Kann Defense: Exchange Variation | |
| May 21, 2022 | Posthuma | 1–0 | Rodriguez Rivera | 2022 Saint Louis Norm Congress - International Master | Zukertort Opening: Nimzo-Larsen Variation | |
| May 21, 2022 | Yu | 0–1 | Posthuma | 2022 Saint Louis Norm Congress - International Master | Queen's Indian Accelerated | |
| May 20, 2022 | Posthuma | 1–0 | Proleiko | 2022 Saint Louis Norm Congress - International Master | King's Indian Attack: Spassky Variation | |
| May 20, 2022 | Lee | ½–½ | Posthuma | 2022 Saint Louis Norm Congress - International Master | Queen's Indian Accelerated | |
| May 19, 2022 | Tokhirjonova | ½–½ | Posthuma | 2022 Saint Louis Norm Congress - International Master | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Jul 2, 2021 | Posthuma | * | Akopian | 49th Annual World Open | King's Indian Defense: Fianchetto Variation, Double Fianchetto Attack | |
| — | Posthuma | ½–½ | Panjwani | Round 6: Posthuma, Joshua - Panjwani, Raja | Lion Defense: Lion's Jaw | |
| — | Posthuma | * | Song | Round 9: Posthuma, Joshua - Song, Edward | Slav Defense: Breyer Variation | |
| — | Noritsyn | * | Posthuma | Round 3: Noritsyn, Nikolay - Posthuma, Joshua | Sicilian Defense: Hyperaccelerated Fianchetto | |
| — | Larry Yang | 0–1 | Posthuma | Round 7: Larry Yang - Posthuma, Joshua | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| — | Kantans | 1–0 | Posthuma | Round 8: Kantans, Toms - Posthuma, Joshua | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |