Roberts, 50, a highly regarded conservative appellate court judge, was approved earlier on Thursday by a vote of 78 to 22, with all of the Senate's 55 Republicans voting in lockstep to support the nominee. They were joined by 22 Democrats and one independent.
Roberts watched the Senate confirmation vote via television in the Roosevelt Room of the White House, as a guest of the president.
In remarks just before the vote, top Senate Republican Senator Bill Frist said Roberts had the makings to become one of the truly great US chief justices.
"Judge Roberts possesses the qualities that Americans expect in the chief justice of its highest court, and the qualifications that America deserves," he said in comments made on the Senate floor.
Many Democrats said Roberts' reputation as a brilliant and fair-minded jurist overrode their concerns about his conservative leanings, but some said they were compelled to vote against him out of fear that he might turn out to be even more conservative than he appears, and could be instrumental in overturning decades of hard-fought gains in civil rights and women's issues.
"Try as I might, I cannot find the evidence to conclude that John Roberts understands the real world impact of court decisions on civil rights and equal rights in this country"
"Try as I might, I cannot find the evidence to conclude that John Roberts understands the real world impact of court decisions on civil rights and equal rights in this country," said Democratic Senator Ted Kennedy before the vote.
Despite the reservation of some Democrats, the party split down the middle on the nomination and throughout weeks of hearings and internal debate, mustered only modest opposition to Roberts, who has been praised as affable and amply qualified candidate.
Robert replaces late Chief Justice William Rehnquist, a conservative, who died earlier this month after a long battle with thyroid cancer.