These voters' needs must be addressed, they said.
The ruling will require that Latino majority congressional districts in the region be redrawn in a way that includes Nueces County and excludes Travis County. Will Hurd, R-Helotes - a huge area along the Mexican border that extends from the El Paso area to the San Antonio area.
Several groups sued Texas in 2011 after claiming that congressional districts were drawn unconstitutionally and were meant to harm minority voters. Texas now has 36 congressional districts, 25 are held by Republicans, and 11 held by Democrats.
Texas can still challenge the decision at the Supreme Court, but the ruling gives Democrats hope that they can compete on a more favorable map in 2018.
In the ruling, the judges wrote the court found the map drawers acted, "with an impermissible intent to dilute minority voting strength", and that "Plaintiffs are still being harmed by the lines drawn".
In the ruling, the judges say Doggett's district was drawn with race as a main factor, in an attempt to minimize the number of Democrat districts.
Texas Republicans did not immediately react to the ruling.
The case examined the composition of several North Texas districts, including charges that "Latino and African American voters in Dallas and Tarrant Counties have been splintered and fragmented in both 2011 and 2013 to diminish their ability to effectively participate in the political process".
In a dissenting opinion, Judge Jerry Smith of the U.S. Fifth Circuit Court of Appeals sharply criticized the Justice Department.
Texas Democrats hailed the ruling a win for voting rights, but the dispute might not be over.
Any appeal from the decision of the three-judge trial court would go directly to the United States Supreme Court.
The ruling comes as the Lone State's Latino population grew, adding four additional congressional seats after the 2010 Census.
The decision could have far-reaching consequences for Texas politics and elections.
"It was obvious, from the start, that the DoJ attorneys viewed state officials and the legislative majority and their staffs as a bunch of backwoods hayseed bigots who bemoan the abolition of the poll tax and pine for the days of literacy tests and lynchings", Smith wrote.
A federal court ruled that the GOP-controlled Texas state legislature racially gerrymandered three congressional districts to blunt the growing influence of minority voters, in violation of the Constitution and the Voting Rights Act (VRA). "And the DoJ lawyers saw themselves as an expeditionary landing party arriving here, just in time, to rescue the state from oppression, obviously presuming that plaintiffs' counsel were not up to the task".