Mohammed Salem al-Zumer was arrested Wednesday in the emirate of Sharjah, the BBC reported.
A UAE activist who wished to remain anonymous said Zumer was arrested for expressing his support for the detained activists.
"He was arrested because of his association with the detainees and his activities online," the activist told the BBC.
The Emirates Center for Human Rights said Zumer's home was searched for more than an hour before he was arrested and his laptop and other equipment were seized during the search.
Government officials have not confirmed Zumer's arrest, but one official was reported to have told Zumer's family he would be released Saturday.