| Challenger - Granby | 07/27 17:00 | 26 | [235] Steven Diez v Tatsuma Ito [171] | 5-7,4-6 | |
| Challenger - Granby | 07/26 18:00 | 25 | Benjamin Sigouin v Tatsuma Ito | 6-7,6-7 | |
| Challenger Gatineau | 07/17 18:40 | 25 | [212] Yuki Bhambri v Tatsuma Ito [170] | 6-3,6-2 | |
| Challenger - Winnipeg | 07/11 18:00 | 25 | Tatsuma Ito v Ronnie Schneider | 2-6,6-7 | |
| Wimbledon Qual | 06/29 10:00 | 46 | [122] Sergiy Stakhovsky v Tatsuma Ito [181] | Cancelled | |
| Wimbledon Qual | 06/28 14:00 | 45 | [181] Tatsuma Ito v Alex De Minaur [243] | 6-2,6-4 | |
| Wimbledon Qual | 06/26 10:45 | 44 | [181] Tatsuma Ito v Matija Pecotic [475] | 6-2,6-2 | |
| Challenger Ilkley Qual | 06/18 12:10 | 46 | [174] Tatsuma Ito v Alex Bolt [439] | 6-3,4-6,4-6 | |
| Challenger Ilkley Qual | 06/17 13:55 | 45 | [174] Tatsuma Ito v Luke Saville [323] | 6-3,5-7,7-6 | |
| ATP Den Bosch | 06/12 12:30 | 25 | [76] Andreas Seppi v Tatsuma Ito [174] | 6-3,3-6,6-3 | |
| ATP Den Bosch Qual | 06/11 11:05 | 46 | [98] Julien Benneteau v Tatsuma Ito [173] | 4-6,4-6 | |
| ATP Den Bosch Qual | 06/10 10:00 | 45 | [185] Soon Woo Kwon v Tatsuma Ito [173] | 6-7,7-5,2-6 | |
| French Open Qual | 05/22 14:10 | 44 | [119] Paul-Henri Mathieu v Tatsuma Ito [173] | 6-7,6-2,6-2 | |
| Challenger - Busan | 05/19 05:20 | 27 | [180] Tatsuma Ito v Vasek Pospisil [106] | 3-6,5-7 | |
| Challenger - Busan | 05/18 08:35 | 26 | Tatsuma Ito v Hong Chung | 6-2,1-6,6-1 | |
| Challenger - Busan | 05/16 03:35 | 25 | [101] Thomas Fabbiano v Tatsuma Ito [180] | 4-6,2-6 | |
| Challenger - Seoul | 05/10 01:30 | 25 | [179] Tatsuma Ito v Marko Tepavac [365] | 2-6,3-6 | |
| Challenger Gimcheon | 05/02 05:55 | 25 | Tatsuma Ito v Duckhee Lee | 6-4,3-6,4-6 | |
| Challenger - Taipei | 04/23 07:55 | 29 | [212] Tatsuma Ito v Yen-Hsun Lu [63] | 1-6,6-7 | |
| Challenger - Taipei | 04/22 05:00 | 28 | [191] Akira Santillan v Tatsuma Ito [212] | 4-6,6-2,5-7 | |
| Challenger - Taipei | 04/21 06:00 | 27 | [99] Konstantin Kravchuk v Tatsuma Ito [212] | 4-6,6-7 | |
| Challenger - Taipei | 04/20 06:00 | 26 | [212] Tatsuma Ito v Lukas Lacko [106] | 6-4,6-4 | |
| Challenger - Taipei | 04/18 03:00 | 25 | [175] Yasutaka Uchiyama v Tatsuma Ito [212] | Retired | |
| ITF Japan F5 | 04/09 07:30 | 29 | Tatsuma Ito v Masato Shiga | 6-4,6-2 | |
| ITF Japan F5 | 04/09 03:30 | 28 | [188] Tatsuma Ito v Yusuke Takahashi [364] | 6-4,6-2 | |
| ITF Japan F5 | 04/07 06:10 | 27 | Tatsuma Ito v Tung-Lin Wu | 6-4,6-4 | |
| ITF Japan F5 | 04/06 03:10 | 26 | Tatsuma Ito v Ryota Tanuma | 6-2,6-4 | |
| ITF Japan F5 | 04/04 04:40 | 25 | [188] Tatsuma Ito v Katsuki Nagao [468] | 7-6,6-4 | |
| Challenger Quanzhou | 03/21 04:50 | 25 | [307] Yuki Bhambri v Tatsuma Ito [171] | 7-6,6-2 | |
| Challenger - Shenzhen | 03/14 06:00 | 25 | Duckhee Lee v Tatsuma Ito | 6-1,5-7,6-4 |