The nations filed briefs late Wednesday in support of civil liberties groups that asked a federal judge to declare Georgia's new law unconstitutional and block it from taking effect.
The filing marks a new phase in the legal showdown that has pitted Georgia's attorneys against groups that had threatened to challenge the law even before it was adopted by lawmakers.
Mexico's move also echoes the legal strategy it pursued to challenge tough new immigration rules enacted by other states. Attorneys representing Mexico filed briefs challenging similar legislation adopted in Arizona and Utah.
Gov. Nathan Deal's office on Thursday declined to comment, but he has praised the legislation as a "responsible step forward" in the absence of federal reform. Earlier this week, Deal urged farmers who claimed workers have been scared away by the new immigration restrictions to hire people on probation to work the fields instead.
The measure, Mexico said, would strain diplomatic relations between the U.S. and Mexico, "interfering with the strategic diplomatic interests of the two countries and encouraging an imminent threat of state-sanctioned bias or discrimination."
Argentina, Brazil, Chile, Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Peru also filed briefs Wednesday in support of the plaintiffs.
Other outside groups have also sought to intervene in the run-up to a highly anticipated hearing scheduled for Monday, when a judge could decide whether to block the law from taking effect. Court officials expect a crush of people to attend and are arranging for a spillover courtroom to hold the crowd.
The Anti-Defamation League filed an amicus brief this week warning that the law could deter Latinos from reporting crimes and create an under class vulnerable to increased hate crimes and violence.
The American Immigration Lawyers Association claims the law forces police to make "highly discretionary judgment calls" about those they should detain for immigration violations.
The filing from Mexico said the country's top officials were closely watching the debate surrounding the Georgia measure.
"Mexico respectfully submits that, if HB 87 is allowed to take effect, it will have a significant and long-lasting adverse impact on U.S.-Mexico bilateral relations, and on Mexican citizens and other people of Latin American descent present in Georgia," it said.