| Challenger Cleveland | 01/31 15:00 | 25 | [404] Alafia Ayeni v Gabriel Diallo [221] | 1-6,1-6 | |
| Australian Open | 01/09 07:50 | 14 | [222] Gabriel Diallo v Aleksandar Vukic [129] | 3-6,4-6 | |
| Challenger Canberra | 01/01 23:00 | 168 | [200] Francesco Maestrelli v Gabriel Diallo [227] | 3-6,7-6,6-4 | |
| Challenger Canberra | 12/31 23:00 | 45 | [227] Gabriel Diallo v Juncheng Shang [192] | 6-3,7-6 | |
| Challenger Drummondville | 11/17 20:30 | 26 | [224] Gabriel Diallo v Charles Broom [383] | 4-6,2-6 | |
| Challenger Drummondville | 11/15 21:00 | 25 | [224] Gabriel Diallo v Kai Wehnelt [222] | 6-4,7-6 | |
| Challenger Calgary | 11/12 20:50 | 28 | [259] Dominik Koepfer v Gabriel Diallo [248] | 7-6,6-1 | |
| Challenger Calgary | 11/11 22:35 | 27 | [248] Gabriel Diallo v Antoine Escoffier [216] | 6-3,5-7,7-5 | |
| Challenger Calgary | 11/10 00:45 | 26 | [140] Juan Pablo Ficovich v Gabriel Diallo [248] | 3-6,2-6 | |
| Challenger Calgary | 11/08 01:00 | 25 | Gabriel Diallo v Julian Ocleppo | 7-6,6-4 | |
| Challenger Las Vegas | 10/26 17:30 | 26 | [148] Juan Pablo Ficovich v Gabriel Diallo [250] | 3-6,7-6,6-4 | |
| Challenger Las Vegas | 10/24 19:20 | 25 | [250] Gabriel Diallo v Enzo Couacaud [183] | 6-4,6-4 | |
| Challenger Fairfield | 10/16 19:00 | 29 | [325] Gabriel Diallo v Michael Mmoh [133] | 3-6,2-6 | |
| Challenger Fairfield | 10/15 19:50 | 28 | Alafia Ayeni v Gabriel Diallo | 3-6,1-6 | |
| Challenger Fairfield | 10/14 23:00 | 27 | [325] Gabriel Diallo v Enzo Couacaud [184] | 7-6,7-5 | |
| Challenger Fairfield | 10/13 23:00 | 26 | [160] Ben Shelton v Gabriel Diallo [325] | 7-5,6-7,3-6 | |
| Challenger Fairfield | 10/11 22:20 | 25 | [325] Gabriel Diallo v Leandro Riedi [252] | 2-6,6-4,6-2 | |
| Challenger Columbus | 09/23 16:15 | 27 | [98] Jordan Thompson v Gabriel Diallo [335] | 6-2,6-1 | |
| Challenger Columbus | 09/22 17:55 | 26 | [335] Gabriel Diallo v Aidan Mchugh [359] | 7-5,6-7,7-5 | |
| Challenger Columbus | 09/20 16:00 | 25 | [497] Strong Kirchheimer v Gabriel Diallo [335] | 4-6,3-6 | |
| Challenger Columbus | 09/20 15:55 | 25 | Yasutaka Uchiyama v Gabriel Diallo | Cancelled | |
| Davis Cup | 09/17 14:00 | - | Laslo Djere v Gabriel Diallo | 6-2,6-2 | |
| Challenger Granby | 08/28 17:00 | 29 | Gabriel Diallo v Juncheng Shang | 7-5,7-6 | |
| Challenger Granby | 08/27 16:00 | 28 | Gabriel Diallo v Hiroki Moriya | 6-3,6-4 | |
| Challenger Granby | 08/26 20:00 | 27 | Aziz Dougaz v Gabriel Diallo | 6-3,3-6,6-7 | |
| Challenger Granby | 08/25 14:00 | 26 | Gabriel Diallo v Cedrik-Marcel Stebe | 6-4,4-6,7-6 | |
| Challenger Granby | 08/24 14:00 | 25 | Dan Martin v Gabriel Diallo | 5-7,1-6 | |
| Challenger Vancouver | 08/17 18:50 | 26 | Ricardas Berankis v Gabriel Diallo | 6-4,6-1 | |
| Challenger Vancouver | 08/15 20:00 | 25 | Gabriel Diallo v Zizou Bergs | 4-6,6-2,7-6 | |
| ATP Montreal | 08/07 15:00 | 19 | Gabriel Diallo v Hugo Gaston | Retired |