Twitter's stock fell nearly 10 percent after hours, to below its post-initial public offering low of $38.80 on November 25.
The San Francisco-based company also said viewers refreshed their "timelines" - Twitter's equivalent of Web pageviews - 157 billion times in the first quarter, slightly fewer than some analysts' estimates.
Twitter Chief Executive Dick Costolo pledged in February to revive user growth after disclosing it had fallen to its lowest rate in years. Its shares have been trading 40 percent below their peak as investors wait to see whether the service could broaden its appeal.
Twitter, however, posted better-than-expected quarterly revenue of $250 million, as its mobile ads drew more viewer responses. The company, which has been steadily refining its targeting capabilities, presents ads based on what it thinks each individual user would be interested in.
Twitter said its advertising revenue per thousand timeline views, a metric that measures the effectiveness of its ads, nearly doubled to $1.44.
Excluding certain items, Twitter broke even against Wall Street expectations of a 3 cent per share loss. But the company said its net loss in absolute terms widened nearly fivefold to $132 million from $27 million a year ago.