Beginning in October 2022, there were widespread calls for his resignation after an audio recording of him and other council members making racist, homophobic, and derogatory remarks was leaked.

His mother married a man of Mexican descent, taking the name Carmen Osorio Núñez, and relocated to San Diego.

[10] De León was investigated by then-state assembly speaker Karen Bass, but did not face any punishment and the vote was later changed.

[12] As a California state senator, De León has been generally regarded as a liberal and describes himself as a "proud progressive.

[14][15] In 2018, the bill passed both houses of the California state legislature and was signed into law by governor Jerry Brown on September 10.

In 2016, De León led the charge in the passage of a package of 11 bills intended to prevent gun violence.

[24] He supported SB 562, a proposed bill to create a single payer health care system in California, which stalled in 2017.

[25] De León authored SB 548, legislation that would make significant investments in child care, with a focus on empowering women in the workforce.

"[28] In 2015, de León co-authored follow-up legislation that requires public high schools teaching health education classes to include sexual assault prevention and strategies on how to build healthy peer relationships in their curricula.

[31] The following day a super PAC created by California political strategists Dave Jacobson and Maclen Zilber was formed to support his candidacy.

[32] On June 5, de León came in second place in the nonpartisan blanket primary with 12% of the total vote, enough to advance to the November general election.

[33][34] De León's 12% was the lowest ever recorded for a candidate who advanced to the general election since California instituted its nonpartisan blanket primary rules in 2016.

In July, De León won the endorsement of the California Democratic Party at their executive board meeting in Oakland.

[40] In 2021, de León advocated against SB 9, which would allow for the construction of duplexes in lots that are zoned as single-family home neighborhoods.

[44] In October 2022, an audio recording of a private 2021 meeting attended by de León, fellow Council member Gil Cedillo, Los Angeles County Federation of Labor President Ron Herrera, and Council president Nury Martinez came to light in which Martinez made racist remarks about the adopted black son of their white City Council colleague Mike Bonin, comparing Bonin's treatment of his son to the way one handles a handbag.

They also used slurs against indigenous Oaxacan people who live in Koreatown, and discussed redistricting in order to break up black voting districts, turning them into Latino ones through the process of gerrymandering.

[45] In the aftermath of the leaked racist recordings by de Leon and others, dozens of prominent politicians, including President Joe Biden and Mike Bonin, called for the resignations of all involved.

[49] On October 26, the City Council unanimously voted 12–0 to formally censure de Léon along with Cedillo and Martinez for their actions.

Prior to the scandal, there had been three unsuccessful attempts to recall de León, on the grounds of his failure to tackle homelessness and adequately support law enforcement.

[55] Running for reelection in 2024, Kevin de León came in second place in the top-two primary, with Ysabel Jurado, a tenants rights attorney and affordable housing activist, coming in first.