The top-ranking Republican in Congress said that he did not agree with the decision.
Joe Arpaio, 85, was found guilty after he defied a court order to stop traffic patrols targeting suspected immigrants.
The former sheriff said his conviction was “a witch hunt by the Obama justice department”.
Republican House of Representatives Speaker Paul Ryan is the latest senior politician to condemn Joe Arpaio’s pardon.
His spokesman said in a statement: “Law enforcement officials have a special responsibility to respect the rights of everyone in the United States. We should not allow anyone to believe that responsibility is diminished by this pardon.”
Other prominent Republican critics include Arizona Senator John McCain and former Florida Governor Jeb Bush. Arizona’s other Republican Senator Jeff Flake also condemned the move as did Democrats and human rights campaigners.
Joe Arpaio’s lawyer Jack Wilenchik said that those critical of his pardon were wrong because he was unfairly prosecuted – there was no jury in his case.
The former sheriff was an eager supporter of Donald Trump’s campaign to become president and backed tougher policies to combat illegal immigration.
In a statement announcing the pardon, his first, President Trump said: “Arpaio’s life and career, which began at the age of 18 when he enlisted in the military after the outbreak of the Korean War, exemplify selfless public service.
“Throughout his time as sheriff, Arpaio continued his life’s work of protecting the public from the scourges of crime and illegal immigration.
“Sheriff Joe Arpaio is now 85 years old, and after more than 50 years of admirable service to our nation, he is a worthy candidate for a presidential pardon.”
Joe Arpaio has said that he may consider running for political office again, despite his age.
He lost a bid for re-election in Arizona’s Maricopa County in November 2016, after 24 years in office.
Joe Arpaio could have faced six months in jail at his sentencing in October.
He served in the US military before he became a police officer – where he quickly acquired a reputation for his anti-immigration stance and tough enforcement tactics.
Prosecutors and Donald Trump’s attorneys delivered opening statements and the first witness was called on…
The House of Representatives has finally approved $61 billion in new US military aid for…
The real estate market in the United States has always been a gauge for economic…
France's first lady Brigitte Macron will be the subject of a biopic series. Production company…
A first glimpse of the new business venture from Meghan Markle has been teased on…
Court has wrapped up for the first day of Donald Trump's long-awaited hush-money trial in…