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After raising $160 million 10 months ago, the $2.8 billion startup Slack wants another $150 million

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Stewart Butterfield, slack
Slack CEO Stewart Butterfield  Wikimedia Commons

Slack, the red-hot messaging startup last valued at $2.8 billion, is in talks to raise another $150 million, the WSJ's Yuliya Chernova reported Wednesday.

The company has raised roughly $340 million so far, including a $160 million Series E round in April 2015.

The new funding round could value Slack as high as $4 billion, according to Bloomberg.

"Slack is doing well. There has always been a great deal of investor
interest in the company and we expect that to continue. However, we
have nothing to announce and nothing else to add at this point," Slack's spokesperson said in an email.

Slack is often called one of the fastest growing business apps in history. Since its official launch just two years ago, Slack has added 2.3 million monthly active users and says it's on track to generate roughly $64 million in annual revenue.

Just last week, Slack CEO Stewart Butterfield said that 20% of all of its monthly active users started using the app for the first time this year.

The new funding would be a reflection of Slack's strong growth and investor confidence in the fast-growing startup. There's been multiple reports about the VC funding environment drying up lately, and the market for tech IPOs is in a holding-pattern.

But the fact that Slack is raising another mega-round, less than a year after raising at a $2.8 billion valuation, in a tough funding environment could be a testament to its healthy growth and financial situation.

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Eugene Kim
Eugene is Business Insider’s Chief Tech Correspondent, where he leads coverage of Amazon. His reporting spans the company’s retail and logistics operations to AWS, Alexa, and its internal culture.Previously, he worked at CNBC, Fortune Magazine Korea, and Japan's Yomiuri Shimbun. He holds degrees from NYU and Columbia University’s Graduate School of Journalism.In 2022, Eugene reported on internal documents indicating that Amazon allegedly used deceptive tactics to enroll customers in Prime and made cancellation difficult. The Federal Trade Commission sued Amazon the following year, citing his reporting. The case ended in a record $2.5 billion settlement in 2025.His work has received multiple honors, including the SF Press Club’s Bay Area Journalism Award and SPJ NorCal’s Excellence in Journalism Award.Eugene lives in the Bay Area. Contact him via email at ekim@bjinnox.com, or Signal, Telegram, or WhatsApp at 650-942-3061. Use a personal email address, a nonwork WiFi network, and a nonwork device; here's our guide to sharing information securely.