Hernández previously developed equipment for full-field digital mammography at Lawrence Livermore National Laboratory.

In October 2011, Hernández, at the urging of President Barack Obama, ran for Congress as a Democrat in California's newly redrawn 10th congressional district in the U.S. House of Representatives.

[9] As a child, Hernández worked alongside his family and other farmworkers throughout the fields of California, harvesting crops and moving from one town to another.

[12] José Hernández participated in Upward Bound during high school, a Federal TRIO program that prepares students for college.

[27] During the summer of 2009, Hernández told the Stockton Record that he would consider not running against fellow Democrat Dennis Cardoza in his Stockton-based district.

[31] Hernández made his first public campaign appearance on January 14, 2012, at a Democratic Candidate Forum in Tracy at the Holiday Inn Express & Suites.

In March 2012, Bell, McAndrews & Hiltachk, a law firm with links to the California Republican Party, sued in Sacramento County Superior Court to block Hernández from describing himself as an "astronaut/scientist/engineer" on the June ballot.

The lawsuit stated that "astronaut is not a title one carries for life"; the election code requires the description to be accurate for the previous calendar year.

On March 29, a Sacramento County Superior Court judge ruled that Hernández could be described as an astronaut on the June 5 primary ballot.

[35] Most of Hernández's campaign funds came from outside his district and many donations came from left-wing political action committees and public employee unions.

"[37] Hernández filed papers to challenge incumbent Democratic Representative Josh Harder in the 9th district in 2022, but ultimately did not run.

[39][40] Hernández owns a 20-acre vineyard near Lodi, California, and in 2021 began bottling wine under the Tierra Luna Cellars label.