Nokia, which earlier this month announced a plan to take over of its French rival Alcatel-Lucent, said the core operating profit at the network unit fell to 85 million euros ($94 million) in the first quarter, or 3.2 percent of sales, from 216 million euros a year earlier.
Analysts in a Reuters poll had on average expected a profit of 226 million euros and a margin of 8.7 percent.
Sales at the networks business were slightly ahead of analyst forecasts, up 15 percent from a year ago at 2.67 billion euros, also topping market consensus of 2.59 billion euros.
The company also specified its full-year networks profitability forecast, saying it expects the unit's non-IFRS operating margins around the midpoint of 8 to 11 percent. In January, it had expected a margin in line with that target range.