"We are very happy to have Aya back home," Trump said, seated alongside Hijazi, who returned from Egypt late Thursday. "It's a great honor to have her in the Oval Office with her brother."
White House press secretary Sean Spicer said Friday that Trump "directly engaged behind the scenes" to secure Hijazi's release and raised the issue with Egyptian President Abdel Fattah el-Sisi.
Spicer said Trump "made clear how important it was to him" that Hijazi be released and returned to the United States.
"Today, the President is proud to be welcoming her back to the White House and happy that she is back home on American soil," Spicer said.
Trump was briefed on Hijazi's case early in his term and directed his national security team to take steps to secure her release, he said.
Earlier Friday, a senior White House official confirmed to CNN that the administration had quietly helped negotiate the release of Hijazi and her husband, who had been detained in Egypt for three years.
A Cairo court on Sunday acquitted Hijazi of child abuse and human trafficking charges after she had spent nearly three years behind bars.
Details of the release, which were first reported by The Washington Post and later confirmed by CNN, include that it was facilitated through meetings between Defense Secretary James Mattis and Egyptian President al-Sissi.
A military aide to Trump escorted Hijazi and her family back to Washington on a military plane, according to the administration official.
According to the Post, Hijaz and her husband landed in Washington on Thursday at 10 p.m. ET and she is scheduled to meet Friday with Trump, his daughter, Ivanka Trump, and his son-in-law and senior adviser Jared Kushner. That meeting is not listed on the official White House schedule.
"As far as the release of the American citizen, she was found innocent in the Egyptian courts, and appropriately she is returned home," Mattis told reporters Friday in Tel Aviv. "We were happy to hear she was found innocent."
He made no reference to US efforts to negotiate Hijazi's release.
Hijazi and her seven co-defendants -- including her husband, Mohamed Hassanein -- worked for a foundation dedicated to aiding Cairo's street children until May 2014 when its offices were raided.
They were accused of child abuse and human trafficking. The other defendants were also found not guilty.
Hijazi's case has garnered international attention over the years -- Human Rights Watch called it a "travesty of justice" in a report released last month and argued that there was virtually no evidence to support the prosecution.