The company said financial markets in the period "provided limited" trading opportunities, adding: "It is impossible to predict market conditions for the rest of the year and therefore too early to draw conclusions about the full-year outcome based on the group's performance over the first three months". There were 97,921 Active Customers in the period, down 4% on the previous quarter.
Plus500's share price fell by over 40% in response.
It means the company's share price has more than halved so far this year as regulatory changes and weak markets hit business.
Plus500 Ltd (LON:PLUS), a leading online service provider for trading Contracts for Differences ("CFDs") internationally, today provides a trading update for the three months ended 31 March 2019.
On its share buyback scheme, the group said: 'The Company repurchased 410,500 shares in the quarter, for a total consideration of $5.5 million.
The company said that a mix of subdued markets, fewer trading opportunities and new regulatory rules conspired to act against growth at the FTSE 250 listed firm.
Plus500 saw average revenue per user fall 60% year on year to 550 U.S. dollars from 1,363 USA dollars, and 64% compared with the previous quarter. Plus500 continued to lead the industry in new customer acquisition, both in absolute numbers and in the efficiency of the marketing spend.
The number of new customers signed up in the first quarter rose by 10% quarter-on-quarter to 21,306, while the average user acquisition cost fell by 17% to $1,230.
In February, Plus500 saw shares drop by almost a third after it warned over full-year profits, blaming a regulatory clampdown across Europe.