Twitter reported a rise in revenue for the three months to September but the pace of growth in active users was the slowest since it joined the stock market in 2013.
Twitter had 320 million average active monthly users, up from 316 million the previous quarter, below investor hopes.
The social networking site reported revenues of $569m, up 58% from $361m during the same period last year.
The company's shares fell 11% after the results announcement.
Competition among social network providers has stepped up.
Advertising revenue was $513m for the period, an increase of 58% from $361m over the prior year.
"We've simplified our roadmap and organization around a few big bets," wrote chief executive Jack Dorsey, "across Twitter, Periscope, and Vine that we believe represent our largest opportunities for growth."
The company also lowered its forecast for fourth quarter revenue to a range between $695 and $710.
Dorsey Return
This was the company's first quarter with Jack Dorsey serving as permanent head, after his return as interim chief executive in June. Dorsey a co-founder of Twitter left in 2008 and founded electronic payment services Square.
Last quarter he took a critical stance to the potential profitability of some Twitter products.
Since Dorsey's return Twitter has laid off more then 300 members of staff and said it plans to use the saving from these cuts to invest in priority products but did not say which products.
Twitter has launched several new commercial partnerships with Bigcommerce, Demandware, and Shopify. The website also launched new advertising tools targeting events and editing several ad campaigns at once.
Dave Lee, North America technology reporter, San Francisco
During tonight's first World Series baseball match - between the Kansas City Royals and the New York Mets - millions of viewers will see an advert from Twitter promoting its 'Moments' feature.
The ad campaign will run into 2016, and is yet another attempt by Twitter to help normal people (i.e. not media geeks, politicians or trolls) find some kind of continued use for Twitter.
Moments, Twitter chief exec Jack Dorsey hopes, will make it much easier for users to follow events. "You don't have to do any of the work," he said.
Baseball is a sport that loves its statistics. So here's a couple about Twitter right now: 307 million monthly active users, with just 3 million added since June.
That's terrible, and they know it. Big money ads alone won't be enough to change that.
