Advertising revenue has also been rising, but by less than was forecast.
Some observers have questioned Mr Musk's commercial judgement in buying Twitter, a platform that despite its high profile has not consistently made high returns.
In the latest quarter it made a profit of $513m (£412m) on revenues of $1.2bn.
Daily active users of the platform rose to 229 million, up from 199 million a year earlier, the company said, publishing its latest financial results.
