The group's Ebitda grew 24% year-on-year to €2.32 billion, while investments totalled €1.19 billion, an increased of 14.1% in the quarter.
Roughly 77% of investments in the three-month period January-March were made in networks (40%) and renewables (37%), the company said.
Iberdrola's renewables business Ebitda grew 13.9% year-on-year to €603.5 million. This was down to better wind conditions compared to 2017 and its installed capacity increasing by 5% to 29.3GW.
The Spanish firm said the Q1 results were in line with expectations for the year. Iberdrola predicted an Ebitda of €9 billion for 2018, with net profit totalling €3 billion.
Iberdrola's majority-owned US subsidiary Avangrid announced a net profit of $243 million for the quarter, up 7% year-on-year.
However, its renewables business unit saw its net profit fall to $50 million, down from $70 million caused by "by less favorable mark-to-market adjustments and the absence of positive discrete tax adjustments recorded in the first quarter of 2017", the subsidiary said.
Elsewhere, Iberdrola has closed a $400 million green loan to refinance the construction of three unspecified wind projects in Mexico.
The loan has a five-year term that can be extended for two years, and was signed with ten banks, Iberdrola said.
It was granted to Iberdrola, through its subsidiary Iberdrola Mexico, on condition that the "funds will finance socially responsible projects in accordance with the sustainable nature of the loan".
Iberdrola has seven operational wind farms with a combined capacity of 548.25MW in Mexico, according to Windpower Intelligence, the research and data division of Windpower Monthly.
The developer has four projects that have not yet been built: the 65MW Esperanza, 116MW Pier I, 220.5MW Pier IV, and 105MW Santiago Eólico sites. It is unclear which of these projects the loan will refinance.