"Jane Sanders came to tents jail, so I invited her inside so I could defend my tent policy. Now waiting for Hillary," Arpaio tweeted, along with a photo of him and Sanders.
Arpaio, who has been dubbed "America's toughest sheriff," endorsed
Republican presidential front-runner Donald Trump in January, citing Trump's plan to "prevent illegal immigration."
Sanders' visit to the jail comes ahead of her husband's rally in Phoenix Tuesday.
Jane Sanders visited "to meet with families who have been victims of Maricopa County Sheriff Joe Arpaio's discriminatory and unconstitutional law enforcement practices," according to the campaign.
Sanders tweeted that Arpaio "showed up unexpectedly" during her visit and she "asked him several questions" about racial profiling, "to which he had no answers."
When he heard Sanders would be paying a visit, Arpaio tweeted that he "adjusted my gun and armed Posse presser @4pm so I could give her a personal tour."
A 2011 Justice Department report
found that Maricopa County "engages in a pattern or practice of unconstitutional policing" and "engages in racial profiling of Latinos; unlawfully stops, detains, and arrests Latinos; and unlawfully retaliates against individuals who complain about or criticize" the county's policies.
"What I saw and heard firsthand today by visiting with the families and seeing tent city was very disturbing," Sanders said in a statement released by the campaign. "Sheriff Arpaio did not even attempt to explain or excuse his inhumane treatment of people of color -- not that he could."
She continued, "That kind of attitude toward our fellow human beings is completely unacceptable, especially in elected officials and those who would seek public office. We all need to stand up and put an end to these egregious human rights abuses."
The jail, located in a remote area in Arizona, was established by Arpaio in 1993 to alleviate prison overcrowding and is known as Tent City because prisoners reside in tents, as opposed to jail cells, in an area known for intense heat.
"He admitted that the temperature in the tents were up to 130 degrees in the summer. He told me he took all meat out of the prisoner's meals," Sanders tweeted, adding that, "Today's visits made it clear that we need real immigration and justice reform to keep families safe."
Arpaio has been under fire by human rights activists for the conditions of the jail for years and a 1997 Amnesty International report
found that incarceration methods in Maricopa County prisons, including Tent City, violate international standards of human rights, while security and environmental hazards make the tents "unsuitable for inmate housing."
In the wake of protests last July, Arpaio's office released a statement defending the jail,
as the sheriff celebrated the facility's 22nd anniversary.
"If Tent City is as bad as critics and activists say, why have four U.S. presidential candidates visited the tents during campaign stops?" Arpaio said. "No presidential candidate would step foot in Tent City if it truly was the cruel and inhumane jail my critics claim it to be."
"It's an excellent, efficient jail that continues to save taxpayers millions," he added.