| ITF W100 Charleston | 05/01 14:00 | 25 | [158] Veronica Cepede Royg v Mari Osaka [347] | 1-6,7-5,6-3 | |
| ITF W100 Charleston | 04/30 15:35 | 54 | [347] Mari Osaka v Sanaz Marand [414] | 7-5,6-4 | |
| ITF W100 Charleston | 04/29 14:00 | 54 | Mari Osaka v Joelle Kissell | 6-1,6-2 | |
| ITF W25 Osprey | 04/25 15:30 | 26 | [254] Ann Li v Mari Osaka [322] | 6-1,6-3 | |
| ITF W25 Osprey | 04/24 19:10 | 25 | Alexandra Perper v Mari Osaka | 6-0,4-6,0-6 | |
| ITF W25 Pelham | 04/11 23:30 | 26 | [319] Mari Osaka v Sesil Karatantcheva [191] | 4-6,4-6 | |
| ITF W25 Pelham | 04/10 16:05 | 25 | [319] Mari Osaka v Kayla Day [367] | 6-3,6-4 | |
| ITF W25 Pelham | 04/09 21:30 | 54 | [319] Mari Osaka v Panna Udvardy [356] | 7-6,6-3 | |
| ITF W25 Pelham | 04/08 15:00 | 54 | Mari Osaka v Epiphany B. Turner | 6-0,6-0 | |
| ITF W80 Palm Harbor | 04/04 17:45 | 26 | [330] Mari Osaka v Kurumi Nara [177] | 6-7,4-6 | |
| ITF W80 Palm Harbor | 04/02 19:25 | 25 | [330] Mari Osaka v Urszula Radwanska [260] | 6-1,7-6 | |
| WTA Miami | 03/21 16:25 | 23 | [205] Whitney Osuigwe v Mari Osaka [338] | 6-2,6-4 | |
| ITF W100 Midland | 01/28 20:40 | 45 | [388] Emina Bektas v Mari Osaka [332] | 6-1,6-4 | |
| WTA Newport Beach | 01/22 18:00 | 24 | [324] Mari Osaka v Katie Volynets [471] | 0-6,0-6 | |
| ITF Women Toronto | 10/31 15:20 | 25 | Bianca Andreescu v Mari Osaka | 6-1,6-1 | |
| ITF Women Saguenay | 10/24 14:00 | 25 | [312] Manon Arcangioli v Mari Osaka [362] | Retired | |
| ITF Women Florence | 10/21 17:00 | 29 | Mari Osaka v Bianca Andreescu | 4-6,6-2,3-6 | |
| ITF Women Florence | 10/20 17:55 | 28 | Katie Volynets v Mari Osaka | 2-6,6-4,3-6 | |
| ITF Women Florence | 10/19 14:00 | 27 | [361] Mari Osaka v Paula C Goncalves [317] | 5-7,6-4,6-1 | |
| ITF Women Florence | 10/18 14:00 | 26 | [256] Ulrikke Eikeri v Mari Osaka [361] | 1-6,3-6 | |
| ITF Women Florence | 10/16 17:55 | 25 | [449] Quinn Gleason v Mari Osaka [361] | 1-6,6-7 | |
| ITF Women Stockton | 10/04 22:30 | 26 | [368] Mari Osaka v Robin Anderson [336] | 5-7,4-6 | |
| ITF Women Stockton | 10/03 20:55 | 25 | [368] Mari Osaka v Maria Sanchez [334] | 6-1,6-3 | |
| WTA Tokyo | 09/15 01:00 | 45 | [344] Mari Osaka v Antonia Lottner [156] | 3-6,6-4,3-6 | |
| ITF Women Montreux | 09/07 13:00 | 27 | [299] Kimberly Zimmermann v Mari Osaka [367] | 7-5,6-4 | |
| ITF Women Montreux | 09/06 08:00 | 26 | [367] Mari Osaka v Martina Trevisan [175] | 6-3,6-2 | |
| ITF Women Montreux | 09/04 09:30 | 25 | [367] Mari Osaka v Monika Kilnarova [304] | 6-2,6-1 | |
| ITF Women Budapest | 08/25 12:40 | 54 | [366] Mari Osaka v Maria Marfutina [491] | 1-6,2-6 | |
| ITF Women Braunschweig | 08/22 09:00 | 25 | [346] Anastasia Zarycka v Mari Osaka [366] | 6-4,7-5 | |
| ITF Women Porto | 07/24 09:30 | 25 | [376] Lisa Sabino v Mari Osaka [348] | 6-2,6-1 |