“It’s become best practice,” Mr. Van Grinsven says, noting that parents can influence their children’s career decisions. Some Northwestern Mutual managers call or send notes to parents when interns achieve their sales goals and let parents come along to interviews and hear details of job offers. They may even visit parents at home.

Mr. Van Grinsven says the efforts have paid off: The number of interns meeting the company’s benchmark for success in sales has risen more than 40% since 2007, a productivity improvement that he attributes in part to more parental support.

In May, Google Inc. GOOG +0.85% held its second annual “Take Your Parents to Work Day,” hosting more than 2,000 parents at its Mountain View, Calif., headquarters. Participation numbers showed that the event was valuable to employees, the company says.

It may be on the rise, but parental involvement in the U.S. doesn’t begin to match countries in Asia and South America, according to a 2013 study from the global accountancy firm PricewaterhouseCoopers LLP.