President Mahinda Rajapaksa swore in Mohan Peiris, a retired attorney general and a legal adviser to the Cabinet, after his nominee was approved by a parliamentary council earlier Tuesday, said presidential spokeswoman Anuradha Herath.
On Sunday, Rajapaksa dismissed Chief Justice Shirani Bandaranayake after a parliamentary committee found her guilty of having unexplained wealth and misuse of power.
Bandaranayake has denied the charges and accused the tribunal of not giving her a fair hearing. Courts have ruled in her favour, but the president and Parliament ignored the rulings.
Peiris has been prominent in defending Rajapaksa's government from allegations of human rights violations and enforced disappearances.
Rajapaksa's critics say appointing a confidante to the post of chief justice gives him control over the judiciary as well as Parliament, where more than two-thirds of the 225 members support him.
The critics also say replacing the chief justice is part of an effort to consolidate the government's power in the hands of the president's family.
Rajapaksa's older brother is the parliamentary speaker, and two of his younger brothers hold the powerful positions of economic development minister and defence secretary. Rajapaksa's eldest son is a lawmaker.
Many prominent lawyers have already said they still recognize Bandaranayake as the chief justice and have written to senior judges urging them not to recognize a new appointee.
Hundreds of policemen guarded the country's main court complex in Colombo, the capital, on Tuesday in an apparent bid to prevent Bandaranayake from entering the courts. Bandaranayake, however, remained at home.
Lawyers supporting Bandaranayake protested her dismissal by blowing out candles in unison in front of the Supreme Court, saying the act symbolized the death of the judiciary. They chanted, "Let's rise against dictatorship."
"The legal community is not ready to accept a puppet appointed by this authoritarian (president)," said Srinath Perera, a lawyer who took part in the protest.