Mexico's Foreign Relations Department said Wednesday it is assisting the 10 Mexican plaintiffs in the suit, filed in El Paso.
The lawsuit claims Walmart "did not take reasonable and necessary measures to protect its customers."
The department did not say what damages the lawsuit seeks. It said plaintiffs include relatives of those killed, wounded victims and relatives of the wounded.
Eight Mexicans were among the 22 people killed in the shooting, while eight other Mexicans were wounded.
Police have said that Patrick Crusius of Dallas confessed to the shooting and that he targeted Mexicans.
Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.