| Dec 21, 2023 | Aram Hakobyan | 1–0 | Joshua Posthuma | Round 8: Aram Hakobyan - Joshua Posthuma | Semi-Slav Defense: Stonewall Defense | |
| Dec 21, 2023 | Joshua Posthuma | ½–½ | Tran Gia Phuc Pham | Round 7: Joshua Posthuma - Tran Gia Phuc Pham | Catalan Opening: Open Defense | |
| Nov 6, 2023 | Jakub Fus | ½–½ | Joshua Posthuma | Round 9: Jakub Fus - Joshua Posthuma | English Opening: Symmetrical Variation | |
| Nov 6, 2023 | Joshua Posthuma | 0–1 | Josiah Stearman | Round 8: Joshua Posthuma - Josiah Stearman | Queen's Gambit Accepted: Normal Variation, Traditional System | |
| Nov 5, 2023 | Luka Budisavljevic | 0–1 | Joshua Posthuma | Round 7: Luka Budisavljevic - Joshua Posthuma | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack | |
| Nov 5, 2023 | Joshua Posthuma | ½–½ | Ekin Baris Ozenir | Round 6: Joshua Posthuma - Ekin Baris Ozenir | Queen's Gambit Accepted: Mannheim Variation | |
| Nov 4, 2023 | Robby Kevlishvili | ½–½ | Joshua Posthuma | Round 5: Robby Kevlishvili - Joshua Posthuma | Sicilian Defense: Löwenthal Variation | |
| Nov 4, 2023 | Joshua Posthuma | 1–0 | Kostya Kavutskiy | Round 4: Joshua Posthuma - Kostya Kavutskiy | King's Indian Defense: Sämisch Variation, Normal Defense | |
| Nov 3, 2023 | Alexander Fishbein | ½–½ | Joshua Posthuma | Round 3: Alexander Fishbein - Joshua Posthuma | Caro-Kann Defense: Main Line | |
| Nov 3, 2023 | Joshua Posthuma | ½–½ | Bach Ngo | Round 2: Joshua Posthuma - Bach Ngo | Indian Defense | |
| Nov 2, 2023 | Joshua Posthuma | ½–½ | Mark Heimann | Round 1: Joshua Posthuma - Mark Heimann | Queen's Gambit Declined | |
| Aug 6, 2023 | David Brodsky | ½–½ | Joshua Posthuma | Round 9: David Brodsky - Joshua Posthuma | Sicilian Defense: Löwenthal Variation | |
| Aug 5, 2023 | Joshua Posthuma | ½–½ | Avi Harrison Kaplan | Round 8: Joshua Posthuma - Avi Harrison Kaplan | English Opening: Symmetrical Variation | |
| Aug 4, 2023 | Joshua Posthuma | 1–0 | Bojanovic Ratko | Round 7: Joshua Posthuma - Bojanovic Ratko | Queen's Pawn Game | |
| Aug 3, 2023 | Kostya Kavutskiy | 0–1 | Joshua Posthuma | Round 5: Kostya Kavutskiy - Joshua Posthuma | Queen's Indian Defense: Kasparov-Petrosian Variation, Kasparov Attack | |
| Aug 2, 2023 | Joshua Posthuma | 0–1 | Dmitry Gurevich | Round 3: Joshua Posthuma - Dmitry Gurevich | Queen's Gambit Declined | |
| Aug 2, 2023 | Nicholas Ladan | 0–1 | Joshua Posthuma | 2023 US Open Championships | Marienbad System | |
| Jun 10, 2023 | Joshua Posthuma | ½–½ | Lazaro Bruzon Batista | Round 6: Joshua Posthuma - Lazaro Bruzon Batista | Benoni Defense | |
| Jun 4, 2023 | Joshua Posthuma | 0–1 | Victor Matviishen | Round 11: Joshua Posthuma - Victor Matviishen | Slav Defense: Breyer Variation | |
| Jun 4, 2023 | Lazaro Batista Bruzon | 1–0 | Joshua Posthuma | Round 3: Lazaro Batista Bruzon - Joshua Posthuma | Caro-Kann Defense | |
| Jun 3, 2023 | Joshua Posthuma | ½–½ | Mateusz Bartel | Round 2: Joshua Posthuma - Mateusz Bartel | Queen's Gambit Declined | |
| Jun 3, 2023 | Evgeny Bareev | 0–1 | Joshua Posthuma | Round 1: Evgeny Bareev - Joshua Posthuma | Indian Defense: Normal Variation | |
| May 29, 2023 | Joshua Posthuma | ½–½ | Eric Liu | 32nd Annual Chicago Open | Old Indian Defense: Normal Variation | |
| May 29, 2023 | Nicholas Ladan | 0–1 | Joshua Posthuma | 32nd Annual Chicago Open | Pseudo Queen's Indian Defense | |
| May 28, 2023 | Joshua Posthuma | 1–0 | Rose Atwell | 32nd Annual Chicago Open | Catalan Opening: Closed | |
| May 28, 2023 | Ryan Amburgy | 1–0 | Joshua Posthuma | 32nd Annual Chicago Open | Slav Defense: Chebanenko Variation | |
| May 27, 2023 | Joshua Posthuma | ½–½ | Tanitoluwa Adewumi | 32nd Annual Chicago Open | Indian Defense: Knights Variation | |
| May 27, 2023 | Dachey Lin | ½–½ | Joshua Posthuma | 32nd Annual Chicago Open | English Opening: Symmetrical Variation, Ultra-Symmetrical Variation | |
| May 26, 2023 | Matthew Wofford | * | Joshua Posthuma | 32nd Annual Chicago Open | ? | |
| Mar 17, 2023 | Anthony Atanasov | ½–½ | Joshua Posthuma | Round 9: Anthony Atanasov - Joshua Posthuma | Caro-Kann Defense: Exchange Variation | |
| Mar 16, 2023 | Joshua Posthuma | 1–0 | Gabor Nagy | Round 8: Joshua Posthuma - Gabor Nagy | Queen's Gambit Declined | |
| Mar 16, 2023 | Mark Plotkin | 0–1 | Joshua Posthuma | Round 7: Mark Plotkin - Joshua Posthuma | Caro-Kann Defense: Endgame Offer | |
| Mar 15, 2023 | Joshua Posthuma | ½–½ | Mike Ivanov | Round 6: Joshua Posthuma - Mike Ivanov | King's Indian Attack: Symmetrical Defense | |
| Mar 15, 2023 | Luis Fernando Ibarra Chami | ½–½ | Joshua Posthuma | Round 5: Luis Fernando Ibarra Chami - Joshua Posthuma | Indian Defense: Normal Variation | |
| Mar 14, 2023 | Joshua Posthuma | 1–0 | Zachary Dukic | Round 4: Joshua Posthuma - Zachary Dukic | King's Indian Attack | |
| Mar 14, 2023 | Nikolay Noritsyn | ½–½ | Joshua Posthuma | Round 3: Nikolay Noritsyn - Joshua Posthuma | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack, Fianchetto Variation | |
| Mar 13, 2023 | Joshua Posthuma | 1–0 | Bator Sambuev | Round 2: Joshua Posthuma - Bator Sambuev | Catalan Opening: Open Defense | |
| Mar 13, 2023 | Victor Mikhalevski | ½–½ | Joshua Posthuma | Round 1: Victor Mikhalevski - Joshua Posthuma | Indian Defense: Normal Variation | |
| Mar 20, 2022 | Joshua Posthuma | ½–½ | Ruiyang Yan | Round 9: Joshua Posthuma - Ruiyang Yan | Catalan Opening: Closed | |
| Mar 20, 2022 | Mike Ivanov | 0–1 | Joshua Posthuma | Round 8: Mike Ivanov - Joshua Posthuma | Caro-Kann Defense | |
| Mar 19, 2022 | Joshua Posthuma | ½–½ | Roberto Martin Del Campo | Round 7: Joshua Posthuma - Roberto Martin Del Campo | Old Indian Defense: Two Knights Variation | |
| Mar 19, 2022 | Brewington Hardaway | 0–1 | Joshua Posthuma | Round 6: Brewington Hardaway - Joshua Posthuma | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Mar 18, 2022 | Joshua Posthuma | 1–0 | James Canty | Round 5: Joshua Posthuma - James Canty | Dutch Defense: Leningrad Variation | |
| Mar 18, 2022 | Vishnu Vanapalli | 0–1 | Joshua Posthuma | Round 4: Vishnu Vanapalli - Joshua Posthuma | English Opening: Anglo-Indian Defense, King's Indian Formation, Double Fianchetto | |
| Mar 17, 2022 | Joshua Posthuma | ½–½ | Oladapo Adu | Round 3: Joshua Posthuma - Oladapo Adu | Queen's Gambit Declined | |
| Mar 17, 2022 | Joshua Posthuma | 1–0 | Nicolas De La Colina | Round 1: Joshua Posthuma - Nicolas De La Colina | King's Indian Defense: Sämisch Variation, Sämisch Gambit | |
| Mar 17, 2022 | Nikolai Andrianov | ½–½ | Joshua Posthuma | Round 2: Nikolai Andrianov - Joshua Posthuma | Pseudo Queen's Indian Defense | |
| Jan 17, 2022 | Joshua Posthuma | ½–½ | Guillermo Vazquez | Round 9: Joshua Posthuma - Guillermo Vazquez | Queen's Gambit Declined | |
| Jan 17, 2022 | Craig Hilby | ½–½ | Joshua Posthuma | Round 8: Craig Hilby - Joshua Posthuma | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Jan 16, 2022 | Joshua Posthuma | 1–0 | Rohan Talukdar | Round 7: Joshua Posthuma - Rohan Talukdar | English Opening: Symmetrical Variation | |
| Jan 16, 2022 | Titas Stremavicius | ½–½ | Joshua Posthuma | Round 6: Titas Stremavicius - Joshua Posthuma | Sicilian Defense: Accelerated Dragon, Maróczy Bind, Gurgenidze Variation | |
| Jan 15, 2022 | Joshua Posthuma | 1–0 | Gauri Shankar | Round 5: Joshua Posthuma - Gauri Shankar | Catalan Opening: Open Defense | |
| Jan 15, 2022 | Jianchao Zhou | 1–0 | Joshua Posthuma | Round 4: Jianchao Zhou - Joshua Posthuma | Queen's Indian Defense: Petrosian Variation | |
| Jan 14, 2022 | Joshua Posthuma | ½–½ | Abhimanyu Mishra | Round 3: Joshua Posthuma - Abhimanyu Mishra | Semi-Slav Defense: Quiet Variation | |
| Jan 14, 2022 | Josiah Stearman | ½–½ | Joshua Posthuma | Round 2: Josiah Stearman - Joshua Posthuma | Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense | |
| Jan 13, 2022 | Anish Vivekananthan | ½–½ | Joshua Posthuma | Round 1: Anish Vivekananthan - Joshua Posthuma | English Opening: Symmetrical Variation, Three Knights, Fianchetto Variation | |
| Jul 3, 2021 | Joshua Posthuma | 1–0 | Mark Paragua | 49th Annual World Open | Semi-Slav Defense: Quiet Variation | |
| Jun 20, 2021 | Viktor Matviishen | 0–1 | Joshua Posthuma | Round 9: Viktor Matviishen - Joshua Posthuma | Queen's Indian Accelerated | |
| Jun 20, 2021 | Joshua Posthuma | 1–0 | Samuel Schmakel | Round 8: Joshua Posthuma - Samuel Schmakel | Catalan Opening: Open Defense | |
| Jun 19, 2021 | Joshua Posthuma | ½–½ | Melikset Khachiyan | Round 6: Joshua Posthuma - Melikset Khachiyan | Slav Defense: Quiet Variation | |
| Jun 19, 2021 | Joshua Posthuma | 0–1 | Andrew Tang | Round 5: Joshua Posthuma - Andrew Tang | Catalan Opening: Open Defense | |
| Jun 18, 2021 | Steven Zierk | ½–½ | Joshua Posthuma | Round 4: Steven Zierk - Joshua Posthuma | Caro-Kann Defense: Exchange Variation | |
| Jun 18, 2021 | Pavlo Vorontsov | 0–1 | Joshua Posthuma | Round 3: Pavlo Vorontsov - Joshua Posthuma | Pseudo Queen's Indian Defense | |
| Jun 17, 2021 | Joshua Posthuma | ½–½ | Titas Stremavicius | Round 2: Joshua Posthuma - Titas Stremavicius | Dutch Defense: Leningrad Variation | |
| Feb 15, 2021 | Joshua Posthuma | ½–½ | Evan Park | 1st Charlotte Masters - Round 6: Joshua Posthuma - Evan Park | Dutch Defense: Leningrad Variation | |
| Feb 15, 2021 | Joshua Colas | 1–0 | Joshua Posthuma | 1st Charlotte Masters - Round 5: Joshua Colas - Joshua Posthuma | Caro-Kann Defense: Tartakower Variation | |
| Feb 14, 2021 | Tianqi Wang | ½–½ | Joshua Posthuma | 1st Charlotte Masters - Round 4: Tianqi Wang - Joshua Posthuma | Caro-Kann Defense: Exchange Variation | |
| Feb 14, 2021 | Joshua Posthuma | 1–0 | Isaac Chiu | 1st Charlotte Masters - Round 3: Joshua Posthuma - Isaac Chiu | Modern Defense: Averbakh System | |
| Feb 13, 2021 | Rochelle Wu | 1–0 | Joshua Posthuma | 1st Charlotte Masters - Round 2: Rochelle Wu - Joshua Posthuma | Trompowsky Attack | |
| Feb 13, 2021 | Joshua Posthuma | 1–0 | Naman Kumar | 1st Charlotte Masters - Round 1: Joshua Posthuma - Naman Kumar | Catalan Opening: Closed | |