WASHINGTON — President Donald Trump has pardoned former sheriff Joe Arpaio following his conviction for intentionally disobeying a judge’s order in an immigration case.

The White House announced the move Friday night, saying the 85-year-old ex-sheriff of Arizona’s Maricopa County was a “worthy candidate” for a presidential pardon.

Joe Arpaio served for 24 years as sheriff of Maricopa County, Ariz., building a national reputation for harsh conditions in his county jail, and for his campaign against undocumented immigrants.

WASHINGTON — President Trump on Friday pardoned Joe Arpaio, the former Arizona sheriff whose aggressive efforts to hunt down and detain undocumented immigrants made him a national symbol of the divisive politics of immigration and earned him a criminal contempt conviction.

In a two-paragraph statement, the White House said that Mr. Arpaio gave “years of admirable service to our nation” and called him a “worthy candidate for a presidential pardon.”

Mr. Trump, who made cracking down on illegal immigration a signature campaign issue and had pressed for local officials to do more to assist federal authorities in rounding up undocumented people, had been openly flirting with the idea of pardoning Mr. Arpaio.

“I won’t do it tonight because I don’t want to cause any controversy,” the president said Tuesday night at a campaign-style rally in Phoenix, after asking, “Was Sheriff Joe convicted for doing his job?”

Mr. Arpaio, 85, served for 24 years as sheriff of Maricopa County, which includes Phoenix, building a national reputation for harsh conditions in his county jail, and for his campaign against undocumented immigrants.

The criminal conviction grew out of a lawsuit filed a decade ago charging that the sheriff’s office regularly violated the rights of Latinos, stopping people based on racial profiling, detaining them based solely on the suspicion that they were in the country illegally, and turning them over to the immigration authorities.

A federal district judge hearing the case ordered Mr. Arpaio in 2011 to stop detaining people based solely on suspicion of their immigration status, when there was no evidence that a state law had been broken. But the sheriff insisted that his tactics were legal and that he would continue employing them.

He was convicted last month of criminal contempt of court for defying the order, a misdemeanor punishable by up to six months in jail.