Companies can require their workers go through arbitration to pursue any legal claims against their employers, rather than go to court or join together in class lawsuits or grievances, the U.S. Supreme Court held today in a 5-4 vote.

The ruling is a major victory for thousands of companies that already require employees to sign arbitration agreements as a condition of their employment. The high court’s endorsement of the agreements will likely encourage many more businesses to set up private...