| ATP Rio De Janeiro | 02/18 21:20 | 25 | [109] Leonardo Mayer v Lorenzo Sonego [52] | 1-6,7-5,4-6 | |
| ATP Buenos Aires | 02/12 00:30 | 25 | [107] Leonardo Mayer v Albert Ramos-Vinolas [42] | 6-4,3-6,5-7 | |
| ATP Cordoba | 02/05 00:05 | 25 | [103] Leonardo Mayer v Jaume Munar [87] | 4-6,3-6 | |
| Australian Open | 01/21 01:45 | 23 | [101] Leonardo Mayer v Tommy Paul [80] | 6-4,4-6,4-6,4-6 | |
| ATP Auckland | 01/14 03:30 | 25 | [100] Leonardo Mayer v Marco Cecchinato [76] | 6-7,7-6,6-7 | |
| ATP Auckland | 01/11 22:00 | 164 | [87] Thiago Monteiro v Leonardo Mayer [88] | 7-6,4-6,6-1 | |
| ATP Auckland | 01/10 22:00 | 64 | [400] Rhett Purcell v Leonardo Mayer [88] | 5-7,6-4,1-6 | |
| Challenger Guayaquil | 11/01 23:00 | 27 | [155] Juan P Varillas v Leonardo Mayer [94] | Retired | |
| Challenger Guayaquil | 11/01 00:35 | 26 | [268] Roberto Quiroz v Leonardo Mayer [94] | 3-6,4-6 | |
| Challenger Guayaquil | 10/29 21:00 | 25 | [204] Andrea Collarini v Leonardo Mayer [94] | 1-6,6-2,4-6 | |
| Challenger Lima | 10/24 19:30 | 26 | [201] Joao Menezes v Leonardo Mayer [95] | 6-4,1-6,6-4 | |
| Challenger Lima | 10/22 23:10 | 25 | [405] Inigo Cervantes v Leonardo Mayer [95] | 2-6,3-6 | |
| Challenger Santo Domingo | 10/10 02:50 | 25 | [368] Guilherme Clezar v Leonardo Mayer [94] | 6-3,1-6,7-6 | |
| Challenger Campinas | 10/03 22:10 | 26 | Thomaz Bellucci v Leonardo Mayer | Walkover | |
| Challenger Campinas | 10/01 20:10 | 25 | [427] Camilo Ugo Carabelli v Leonardo Mayer [97] | 6-7,4-6 | |
| Challenger Buenos Aires | 09/28 15:20 | 28 | [166] Facundo Bagnis v Leonardo Mayer [100] | 6-2,3-6,6-3 | |
| Challenger Buenos Aires | 09/27 22:25 | 27 | [100] Leonardo Mayer v Juan P Ficovich [352] | 6-1,6-7,7-6 | |
| Challenger Buenos Aires | 09/26 21:30 | 26 | Leonardo Mayer v Facundo D Acosta | 7-6,6-3 | |
| Challenger Buenos Aires | 09/25 20:30 | 25 | [100] Leonardo Mayer v Federico Zeballos [258] | 7-5,6-1 | |
| US Open | 08/27 22:00 | 23 | [104] Antoine Hoang v Leonardo Mayer [95] | 3-6,6-2,6-7,6-1,6-3 | |
| ATP Kitzbuhel | 07/30 09:00 | 25 | [75] Pablo Andujar v Leonardo Mayer [81] | 3-6,6-3,6-2 | |
| ATP Hamburg | 07/22 16:30 | 25 | [51] Leonardo Mayer v Rudolf Molleker [150] | 6-7,4-6 | |
| ATP Umag | 07/19 15:30 | 27 | [32] Laslo Djere v Leonardo Mayer [60] | 6-4,6-7,6-3 | |
| ATP Umag | 07/17 15:15 | 26 | [142] Jiri Vesely v Leonardo Mayer [60] | 6-3,4-6,4-6 | |
| ATP Umag | 07/16 17:30 | 25 | [79] Pablo Andujar v Leonardo Mayer [60] | 1-6,5-7 | |
| Wimbledon | 07/03 11:25 | 24 | [59] Leonardo Mayer v Hubert Hurkacz [48] | 7-6,1-6,6-7,3-6 | |
| Wimbledon | 07/01 11:25 | 23 | [92] Ernests Gulbis v Leonardo Mayer [59] | 1-6,6-7,2-6 | |
| ATP Eastbourne | 06/25 10:00 | 25 | Jay Clarke v Leonardo Mayer | Cancelled | |
| French Open | 06/02 11:30 | 26 | [68] Leonardo Mayer v Roger Federer [3] | 2-6,3-6,3-6 | |
| French Open | 05/31 13:30 | 25 | [252] Nicolas Mahut v Leonardo Mayer [68] | 6-3,6-7,4-6,6-7 |