Pandikar Amin Mulia, the speaker of Malaysia's lower house of parliament, said Anwar will be formally sworn in as legislator on Thursday.
This will allow Anwar, a former deputy prime minister and finance minister, to attend the tabling of the annual budget in parliament on Friday by Abdullah Ahmad Badawi, Malaysia's prime minister.
His return to mainstream politics after a decade is expected to boost the opposition voice in parliament led by a loose coalition known as Pakatan Rakyat, or People's Alliance.
"We will all be there to welcome Anwar as the leader of the opposition and the parliament will be very different with his voice," Tian Chua, Keadilan's information chief, told AFP on Wednesday.
"It is a real morale boost for the Pakatan Rakyat in parliament."
Anwar's landslide victory on Tuesday will not tip the balance of national power but he has vowed to topple the government and become the next prime minister with a promise for change.
He claims there are enough MPs from the ruling Barisan Nasional coalition who are wiling to join him to form a new government by mid-September.
He needs the support of 30 defectors to make this happen.
Last month Anwar's wife, Wan Azizah Wan Ismail, who is also Keadilan president, resigned from the Permatang Pauh seat to make way for him to contest.
|Anwar says the new sodomy charge is a political conspiracy [EPA]
Anwar's convincing win comes despite a new charge of sexual misconduct for allegedly sodomising a male aide early this year.
He says the charges are part of a politically-motivated smear campaign by the government.
Under Malaysian law, sodomy is illegal even if consensual, and a conviction could see Anwar jailed for up to 20 years.
Anwar is scheduled to appear in court on September 10 to deny charges of sexual misconduct, which he says is a government conspiracy similar to that mounted against him 10 years ago.
In 1998 Anwar was charged with sodomy and corruption which led to his sacking from government and political office.
He was later convicted on both charges and served six years in jail before the sodomy conviction was overturned in 2004. The conviction for corruption remains.
Anwar has maintained that Mahathir Mohamad, the former Malaysian prime minister who was his long-time mentor, had framed him in 1998 to prevent a power struggle.