Alongside league goals leader Vela and former Manchester United teammates Rooney and Nani in MLS' showcase event are Zlatan Ibrahimovic and Jonathan dos Santos from LA Galaxy, veteran Sporting KC defender Graham Zusi and Atlanta United goalkeeper Brad Guzan.
The remaining slots on the MLS All-Star Team, set to face 10-time La Liga champions Atletico Madrid on July 31, will be announced at a later date and be made up of two commissioner's picks from Don Garber with the rest of the side filled out by Orlando City coach James O'Connor.
Last year's MLS All-Stars lost on penalties to Serie A champions Juventus after the match finished 1-1 in regular time.
FULL FAN XI:
Goalkeeper: Brad Guzan (Atlanta United)
Defenders: Leandro González Pírez (Atlanta United), Walker Zimmerman (Los Angeles Football Club), Graham Zusi (Sporting Kansas City)
Midfielders: Ezequiel Barco (Atlanta United), Jonathan dos Santos (LA Galaxy), Gonzalo "Pity" Martínez (Atlanta United), Nani (Orlando City SC)
Forwards: Zlatan Ibrahimović (LA Galaxy), Wayne Rooney (D.C. United), Carlos Vela (Los Angeles Football Club)