"They are with their families now. Earlier, they were questioned by the [Bahraini] prosecution and then allowed to go home," member of parliament Muhammad Khalid said on Saturday.
"No measure was taken against them, it was a routine legal procedure," Khalid, an outspoken supporter of Bahraini detainees at Guantanamo, said after meeting the three men.
The three were among six Bahrainis held with about 500 others at the US military base in Cuba after the 2001 US-led invasion of Afghanistan.
Bahrain's Information Minister Muhammad Abd al-Ghaffar Abd Allah earlier identified the three released men as Adil Kamil Haji, Abd Allah al-Nuami and Salman Ibrahim al-Khalifa - a member of the royal family.
However, three other Bahrainis are still imprisoned at the camp including Jumah al-Dossari who reportedly attempted suicide in mid-October, Aljazeera reported.
Plight of detainees
The minister said King Hamad bin Isa al-Khalifa had raised the plight of the Bahraini detainees with US officials during a visit to Washington.
Saudi state media said a Saudi detainee, Majid al-Shamri, had returned to Saudi Arabia on Saturday.
The four men returned a day after five Kuwaitis held in Guantanamo were released.
The Pentagon has said more than 250 detainees have left Guantanamo after a review of their cases and that approximately 500 remained.
Bahrain hosts the headquarters of the US Navy's Fifth Fleet.