Silicon Valley has a diversity problem, one that even Tristan Walker’s 4-year-old son could see.

In 2018, after making a trip to the supermarket with his father in Palo Alto, Calif., Mr. Walker’s son observed, “Palo Alto is where all the white people are.”

It was a moment that struck Mr. Walker, who is Black, not just as a father—but as a CEO. As the head of Walker & Co. Brands, a startup making personal-care products for people of color, he’d noticed it was sometimes hard to recruit people to come to Silicon Valley. The area was expensive, and not particularly diverse. Mr. Walker had been drawn there in 2008 and worked at both Twitter Inc. and Foursquare Labs Inc., but increasingly, he was seeing its limitations.

“We definitely lost out on compelling talent,” says Mr. Walker, 36 years old. He decided to move his family—and his company—to the majority-Black city of Atlanta instead.

In recent years, companies have moved their headquarters out of the suburbs and downtown to court younger workers. Now more companies are adding new office footprints as a way to recruit ethnically diverse talent, too. Atlanta, in particular, has drawn a number of boldfaced names, many in tech. Microsoft Corp. is investing $75 million in an Atlanta facility it says will create 1,500 jobs. Alphabet Inc.’s Google is investing more than $25 million there this year, expanding its existing three-floor office to a new location where the company will eventually occupy 19 floors.