Investigators arrested Awar as he returned from Putrajaya, south of Kuala Lumpur, said his personal lawyer, Siva Rasah.
This is the second time Anwar is facing sodomy charges. He spent six years in prison after being convicted on corruption charges in 1999 and on sodomy charges involving his wife's former driver in 2000. Malaysia's highest court overturned the sodomy conviction and ordered him released from prison in 2004.
While his sodomy conviction was overturned, the corruption conviction never was -- barring him from running for office again until this year.
The ban expired in April but it meant Anwar could not contest the March general elections. He can re-enter Parliament through a by-election, which would make him eligible to become prime minister, a post he has openly aspired to fill.
A loose coalition of opposition parties -- with Anwar at the helm -- won 82 of 222 parliamentary seats in elections in March. It was only the second time in the country's history that the ruling party failed to gain the two-thirds majority needed to amend Malaysia's constitution.
Even as he was preparing to contest a by-election, the ruling coalition has sprung a surprise on him with the new sodomy charge.
A 23-year-old male aide has accused Anwar, 60, of sodomizing him at a luxury apartment in June. Anwar has said the allegations are meant to tamp down his political gains.
"This is a trick to deflect from the problem of corruption and mismanagement of the economy," Anwar told CNN.
Anwar, who was released on bail earlier Thursday, said his arrest and the whole investigation is being conducted by the same police officials whom, he claims, hid evidence that could have cleared him in his sodomy-related conviction in 1999.
The opposition leader said he was ambushed Wednesday by police when he was trying to turn himself in, strip searched, and interrogated for more than five hours.
"How do you expect me to get justice when the police have resulted to these very crude and unprofessional ways?" Awar asked. "I have not received a police report until this day. According to the law that document should be a public document. I cannot even verify that there is a complainant in the first place."
Anwar said that during the entire interview, police never talked about any evidence in the case. They also asked for a blood sample -- the same tactic they used 10 years ago to fabricate DNA evidence against him, Anwar charged.
Anwar, a former deputy premier many believed to be the heir apparent to former Prime Minister Mahathir Mohamad, has long said the past charges against him were politically motivated. The investigating officer in his original sodomy case was Malaysia's chief of police and the prosecutor was the nation's attorney general.
He had left prison in a wheelchair due to injuries he blamed on a 1998 beating by Malaysia's then-police chief.
But Malaysian Home Affairs Minister Syed Hamid Albar maintained there was nothing political about Anwar's arrest.
But certainly Anwar could not be above the law; the minister said.