MLS
USA
| Referee | Games |  |  | Cards per game |
|---|
| Elijio Arreguin | 5 | 25 | 1 | 5.2 (5.0 / 0.2) | |
| Malik Badawi | 17 | 61 | 3 | 3.8 (3.6 / 0.2) | |
| Fotis Bazakos | 12 | 44 | 2 | 3.9 (3.7 / 0.2) | |
| Nabil Bensalah | 1 | 5 | 0 | 5.0 (5.0 / 0.0) | |
| Serhiy Boiko | 23 | 99 | 7 | 4.6 (4.3 / 0.3) | |
| Allen Chapman | 25 | 82 | 3 | 3.4 (3.3 / 0.1) | |
| Alexis Da Silva | 20 | 91 | 1 | 4.7 (4.6 / 0.1) | |
| Marcos de Oliveira | 18 | 66 | 0 | 3.7 (3.7 / 0.0) | |
| Sergii Demianchuk | 10 | 48 | 1 | 4.9 (4.8 / 0.1) | |
| Marcos DeOliveira II | 2 | 10 | 0 | 5.0 (5.0 / 0.0) | |
| Joe Dickerson | 12 | 50 | 2 | 4.4 (4.2 / 0.2) | |
| Greg Dopka | 2 | 7 | 0 | 3.5 (3.5 / 0.0) | |
| Filip Dujic | 24 | 102 | 4 | 4.5 (4.3 / 0.2) | |
| Ismail Elfath | 2 | 4 | 0 | 2.0 (2.0 / 0.0) | |
| Ricardo Fierro | 16 | 64 | 6 | 4.4 (4.0 / 0.4) | |
| Drew Fischer | 19 | 72 | 0 | 3.8 (3.8 / 0.0) | |
| Timothy Ford | 9 | 48 | 4 | 5.7 (5.3 / 0.4) | |
| Jon Freemon | 21 | 102 | 3 | 5.0 (4.9 / 0.1) | |
| Guido Gonzales Jr. | 17 | 74 | 1 | 4.5 (4.4 / 0.1) | |
| Guido Gonzales Jr. | 5 | 17 | 1 | 3.6 (3.4 / 0.2) | |
| Jorge Gonzalez | 1 | 1 | 0 | 1.0 (1.0 / 0.0) | |
| Lorenzo Hernandez | 14 | 67 | 1 | 4.9 (4.8 / 0.1) | |
| Ekaterina Koroleva | 2 | 8 | 0 | 4.0 (4.0 / 0.0) | |
| Pierre-Luc Lauziere | 19 | 85 | 3 | 4.7 (4.5 / 0.2) | |
| Jair Marrufo | 18 | 56 | 2 | 3.2 (3.1 / 0.1) | |
| Rosendo Mendoza | 20 | 108 | 6 | 5.7 (5.4 / 0.3) | |
| Ricardo Montero | 15 | 59 | 1 | 4.0 (3.9 / 0.1) | |
| Abdou Ndiaye | 1 | 6 | 0 | 6.0 (6.0 / 0.0) | |
| Ismir Pekmic | 15 | 77 | 2 | 5.2 (5.1 / 0.1) | |
| Alyssa Pennington | 1 | 8 | 0 | 8.0 (8.0 / 0.0) | |
| Tori Penso | 16 | 66 | 1 | 4.2 (4.1 / 0.1) | |
| Chris Penso | 17 | 75 | 3 | 4.6 (4.4 / 0.2) | |
| Michael Radchuk | 1 | 4 | 0 | 4.0 (4.0 / 0.0) | |
| Victor Rivas | 20 | 89 | 5 | 4.7 (4.4 / 0.3) | |
| Natalie Simon | 1 | 5 | 0 | 5.0 (5.0 / 0.0) | |
| Lukasz Szpala | 14 | 49 | 0 | 3.5 (3.5 / 0.0) | |
| Ramy Touchan | 5 | 25 | 0 | 5.0 (5.0 / 0.0) | |
| Rubiel Vazquez | 22 | 81 | 1 | 3.7 (3.7 / 0.0) | |
| Michael Venne | 1 | 5 | 1 | 6.0 (5.0 / 1.0) | |
| Armando Villareal | 11 | 40 | 2 | 3.8 (3.6 / 0.2) | |
England