Musicians Jennifer Lopez, Ricky Martin and Lin-Manuel Miranda gave their backing to the letter, which called on those outside the Latino community to "speak out loudly against hate."
"If you are feeling terrified, heartbroken and defeated by the barrage of attacks on our community, you are not alone," said the letter, addressed to the Querida Familia Latina (Dear Latino Family) and published in the New York Times, La Opinion and other newspapers.
The letter followed a shooting in the predominantly Latino border city of El Paso, Texas on Aug. 3 that killed 22 people and is believed to have been racially motivated, as well as the arrest of 680 people in immigration raids last week on seven agricultural processing plants in Mississippi.
Both followed accusations that U.S. President Donald Trump has stoked racial divisions with his rhetoric and his crackdown on immigration at the U.S. border with Mexico.
"We will not be broken. We will not be silenced. We will continue to denounce any hateful and inhumane treatment of our community. We will demand dignity and justice," the letter said.
It called on allies of the Latino community to "speak out loudly against hate, to contribute your resources to organizations that support our community, and to hold our leaders accountable."
Former "Desperate Housewives" star Longoria said in a statement that the U.S. is facing "a moral crisis ... and we chose to use this moment to raise our voices and speak up."The letter was signed by many of the leading Latino voices and activists in United States, including veteran labor leader Dolores Huerta, novelist Sandra Cisneros and Voto Latino political group president Maria Teresa Kumar.