- Mike Magee - LA
- Kenny Mansally - NE
- Justin Mapp - CHI
- Peri Marosevic - FCD
- Matt Marquess - KC
- Jesse Marsch - CHV
- Chad Marshall - CLB
- Tyrone Marshall - SEA
- Gonzalo Martinez - DC
- Pablo Mastroeni - COL
- Clint Mathis - RSL
- Gerson Mayen - CHV
- Matthew Mbuta - NY
- Brian McBride - CHI
- Dax McCarty - FCD
- Brandon McDonald - SJ
- Rauwshan McKenzie - KC
- Devon McTavish - DC
- Domenic Mediate - DC
- Carlos Mendes - NY
- Stefani Miglioranzi - LA
- Ryan Miller - DC
- Adam Moffat - CLB
- Fredy Montero - SEA
- Drew Moor - COL
- Javier Morales - RSL
- Alejandro Moreno - CLB
- Jaime Moreno - DC
- Kurt Morsink - KC
- Yura Movsisyan - RSL
- Brian Mullan - HOU
- Richard Mulrooney - HOU
- Mike Munoz - LA
- Chance Myers - KC