McClintock was born in White Plains, New York, and graduated in 1978 from the University of California, Los Angeles (UCLA) with a degree in political science.

[5] In 1982, at age 26, McClintock ran for California's 36th State Assembly district, then based in Thousand Oaks, after redistricting.

[16] In 2008, McClintock voted against Proposition 2, which prohibits confining calves, pigs and hens in small cages in which they cannot extend their limbs.

[20] In the general election, he lost to Kathleen Connell, former Special Assistant to Los Angeles Mayor Tom Bradley and Director of the L.A. Housing Authority, 48%–46%, with three other candidates receiving the other 6% of the vote.

He also cracked 20% or higher in several other counties: Mariposa (23%), Tuolumne (22%), Tehama (21%), Calaveras (20%), Madera (20%), Modoc (20%), Shasta (20%), San Joaquin (20%), and Ventura (20%).

[26] After redistricting, McClintock retired from the Assembly to challenge Democratic U.S. Representative Anthony C. Beilenson in California's 24th congressional district.

He won the nine-candidate Republican primary with a plurality of 34% of the vote, beating second-place finisher Sang Korman by 11 points.

The California Constitution requires state senators to maintain their legal residence in the district they represent.

[29] Upon McClintock's entry into the race, fellow Republicans Rico Oller and Eric Egland withdrew from the primary and endorsed him.

[32] The Democratic nominee was retired Air Force Lt. Col. Charles D. (Charlie) Brown, who had run an unexpectedly strong race against Doolittle in 2006.

[39] For his first two terms, McClintock represented a district covering the northeast corner of California, from the eastern suburbs of Sacramento to the Oregon border.

The reconfigured 4th was as strongly Republican as its predecessor, and McClintock was reelected to a third term, defeating Uppal 61%–39% in the general election.

[41] McClintock was reelected, finishing first in California's "top two" primary and defeating moderate Republican challenger National Guard Major Art Moore in the general election, 60%–40%.

[42] McClintock again finished first in the primary and defeated Democrat Robert W. Derlet, a physician, environmentalist and retired UC Davis professor, in the general election, 63%–37%.

[46] In 2011, he voted against the National Defense Authorization Act for Fiscal Year 2012 due to a provision that would allow the government and the military to indefinitely detain American citizens and others without trial.

In 2009, McClintock signed a pledge sponsored by Americans for Prosperity promising to vote against any global warming legislation that would raise taxes.

[49] He voted against the first version of the bill, displeased with the removal of deductions related to medical expenses, student loan interest, and casualty loss.

He expressed concern about the bill's impact on the budget deficit and anticipated that it would be addressed "by spending reforms this coming year.

[51] After Trump pulled 1,000 U.S. troops from Kurdish-held territory on the Syrian border south of Turkey in 2019, a bipartisan resolution passed the House, 354–60, that condemned him for abandoning those U.S. allies that would allow the Islamic State of Iraq and the Levant (ISIL) to reestablish and regroup its forces, and allow the Turks to attack the Kurds.

[52] In 2020, McClintock was the sole House Republican to cosponsor the Ending Qualified Immunity Act, which was proposed in response to the murder of George Floyd and resultant widespread protests.

[53] The act was introduced by Justin Amash and Ayanna Pressley and cosponsored by 62 House Democrats in addition to McClintock.

[56][57][58] Despite making a speech supporting holding Merrick Garland in contempt of Congress for the federal prosecution of Donald Trump, he would vote against holding him in contempt for refusing to release the audio files of the Hur interviews in the Joe Biden classified documents incident.

[61] The bill was a reaction to the United States Forest Service's decision to pursue a "new regulation to demand that water rights be transferred to the federal government as a condition for obtaining permits needed to operate 121 ski resorts that cross over federal lands.

The lawsuit was called a "seditious abuse of the judicial process" by the attorney general of Pennsylvania,[69] and "simply madness" by 2012 Republican presidential nominee Mitt Romney.

[70] House Speaker Nancy Pelosi issued a statement that called signing the amicus brief an act of "election subversion.

"[78] In 2020, McClintock was one of five House Republicans to vote for the Marijuana Opportunity Reinvestment and Expungement (MORE) Act to legalize cannabis at the federal level.

[83][84] In September 2021, McClintock was among 75 House Republicans to vote against the National Defense Authorization Act of 2022, which contains a provision that would require women to be drafted.

[88] In 2020, McClintock voted against the National Defense Authorization Act of 2021, which would prevent the president from withdrawing soldiers from Afghanistan without congressional approval.

[90][91] In July 2021, McClintock was one of five House Republicans to vote against a bill that allocates $2.1 billion for Afghan visas and Capitol Hill security.

[96] McClintock voted against the Further Consolidated Appropriations Act of 2020 which authorizes DHS to nearly double the available H-2B visas for the remainder of FY 2020.