One of the technology world’s biggest names has given a boost to shares of Care.com Inc., an online marketplace for nannies and other caregivers.

Google Capital, an investment arm of tech giant Alphabet Inc., paid $46.4 million to become the largest shareholder in Waltham-based Care.com, the companies announced Wednesday.

The investment is Google Capital’s first in a publicly traded company. It also owns stakes in private tech companies such as job-rating website Glassdoor Inc. and fantasy sports company FanDuel Inc.

The news drove Care.com stock to nearly $12 per share in after-hours trading, more than 40 percent above the stock’s closing price. Care.com shares hadn’t risen above $9.49 in the past year, after reaching $28.71 per share shortly after its initial public offering in 2014.

Care.com also said it used some of the Google investment to repurchase 3.7 million shares from Matrix Partners, a Cambridge-based venture capital firm, for $30.5 million.

Buying back the stock allowed Care.com to limit other investors’ dilution from the Google stake, chief executive Sheila Marcelo told The New York Times. Care.com and Matrix did not return messages seeking comment.

In a news release, Marcelo praised the operating experience of Google Capital’s Laela Sturdy, who joins the Care.com board of directors. Sturdy said she was already familiar with Care.com because Google had used the company’s business-focused service for several years.

“I’ve been able to see first-hand how Care.com’s innovative mobile platform and enterprise solution – Care@Work – helps families search for caregivers and get much needed back-up care services,’’ Sturdy said in a news release.

Care.com said Google Capital’s stake was comprised of a newly authorized set of convertible preferred stock, with an initial conversion price of $10.50 and a 5.5 percent annual dividend in the first seven years.

The company raised $91 million in its IPO in January 2014. In addition to childcare, it also allows users to search for and hire home health care nurses, dog walkers, and other care providers.

Care.com has drawn some criticism for the thoroughness of its background checks, prompted in part by the case of Stephanie Lee Fox of Randolph, who was still on probation when she registered as a nanny on Care.com.

Fox pleaded guilty last year to federal bank fraud charges for ­stealing more than $280,000 from a Boston couple who had hired her to care for their two children.

Curt Woodward can be reached at curt.woodward@globe.com.