The chamber approved him to replace Alex Acosta with a party-line vote of 53-44. Acosta resigned in July amid increasing scrutiny over a plea agreement he helped negotiate with financier Jeffrey Acosta.
Scalia was a partner in the Washington, D.C., law firm Gibson, Dunn & Crutcher.
During his confirmation hearing earlier this month, Scalia addressed criticism from Democrats about his background representing corporate interests as an attorney. Sen. Patty Murray, D-Wash., cited Scalia's role in striking down an Obama-era fiduciary rule.
The rule would have required advisers on tax-privileged retirement accounts to act in their clients' best interest, but Scalia challenged the rule, arguing it involved a regulatory change that only Congress could approve. A federal court agreed, vacating the rule last year.
Murray said that the move put "billions" of workers' retirement savings in jeopardy.
"It was a common-sense rule that protected workers retirement savings by simply requiring financial advisers to put their clients' interests ahead of their own," she said.
Scalia defended himself, saying that he could remain impartial, and pointing out his time as the Labor Department solicitor during the Bush administration.
"Then, as now, I was coming to the department from the private sector, where I had advised and represented businesses regarding employment matters," he said. "But once at the department, I had new clients, new responsibilities and, above all, I had a public trust. I am proud of the actions I took before as solicitor to further the department's mission."
Sommer Brokaw contributed to this report.