Valdez was born and raised in San Antonio, as the youngest of eight children of Mexican-American migrant farm worker parents.

[2][3] Prior to entering law enforcement, Lupe Valdez was an officer in the United States Army Reserve, where she attained the rank of captain.

[citation needed] Her law enforcement career began as a jailer, first in a county jail and then in a federal prison.

The jail had failed inspections because of poor sanitation conditions which endanger prisoners, many of whom have not ultimately been found to be guilty of any crime and are merely being held pending being formally charged or, released; a failing smoke evacuation system, unacceptable medical care, and a lack of sufficient guards to meet the legally required guard-to-inmate ratio.

[citation needed] In 2015, Valdez "changed policies on holding immigrants in the Dallas County jail for federal officials once the person is past his or her release date.

People who committed minor offenses aren’t held for up to an additional 48 hours for agents of U.S. Immigration and Customs Enforcement, or ICE."

This brought a warning from Governor Greg Abbott to "back down from a policy change on federal immigration detention requests.

The run-off occurred on May 22, 2018, resulting in Valdez's victory and making her the first Latina and first openly gay person nominated for governor by a major party in the state.