BEIJING—Alibaba Group Holding Ltd. is investing in Snapchat Inc. in a deal that values the messaging company at $15 billion, in the latest sign of escalating valuations for technology startups.

The Chinese e-commerce giant has invested $200 million in Snapchat, according to two people familiar with the transaction. The deal values Snapchat at $15 billion, one of those people said.

That valuation marks a significant increase from previous investments. Snapchat raised funds from at least two investors, Yahoo Inc. and venture-capital firm Kleiner Perkins Caufield & Byers, in a round of funding that valued the messaging startup at $10 billion last year. Other investors include Benchmark, General Catalyst Partners, Institutional Venture Partners, Lightspeed Venture Partners, Coatue Management LLC and DST Global.

In July, The Wall Street Journal reported that Alibaba had held talks with Snapchat. One of the people familiar with the latest deal said Alibaba’s interest had cooled then been rekindled recently.

Snapchat has attracted significant investor attention in part because of the ephemeral nature of its messages. Its text and photo messages disappear after a certain amount of time, limiting the possibility that content will come back to haunt the user. It has become one of the world’s most-valuable startups by market valuation, according to a Wall Street Journal analysis. People who have been briefed on its internal metrics say it has more than 100 million users.