The 80-year-old Rehnquist, the second-oldest of the nine members of the court, is expected back on the bench Monday when the court returns from a two-week break. A court spokesman announced his release from National Naval Medical Center in suburban Bethesda, Md.
He underwent a tracheotomy last Saturday at the hospital at as part of his cancer treatment.
The type of thyroid cancer, how advanced it is and Rehnquist's prognosis have not been disclosed. Cancer of the thyroid, a gland in the neck that produces hormones to help regulate the body's use of energy, is generally treatable but can be more aggressive in older people.
The court spokesman would not say if Rehnquist participated in Friday's closed-door meeting of the justices, to consider the latest appeals.
Justice Clarence Thomas had told University of Kansas law students on Thursday that he expected the chief justice back at the court "as unforgiving as ever."
He said justices have a tendency to work even when they're sick, citing justices Sandra Day O'Connor and Ruth Bader Ginsburg as examples. Like Rehnquist, both have battled cancer.
"It's a place where people work as if they're paid by the hour," Thomas said.
Even from the hospital, Rehnquist was apparently participating this week.
On Tuesday, the Supreme Court refused to put independent presidential candidate Ralph Nader on the ballot in the battleground state of Ohio. The court's announcement indicated that all the justices took part in that decision.
The high court also agreed Wednesday to let Philip Morris USA delay paying $10.5 million in damages to a former smoker while the company contests the amount. Rehnquist apparently voted in that case as well.
"He is a very resilient, robust, strong-willed man," said Washington attorney Charles Cooper, who clerked for Rehnquist. "He's dedicated to his work and his responsibilities. In keeping with that dedication, he would continue (work) unless completely prevented from it."