Gamesa will service 244.65MW - all of SER's Gamesa turbines in Italy - for four and a half years.
The Spanish firm will maintain 33 G87-2MW, nine G80-2MW and 189 G52-850kW turbines across 11 projects.
SER is a joint venture formed between Iberdrola and Italian oil group API Holding. It was formed in 2007 with the aim of developing 350MW of wind projects.
O&M servicing is a large part of Gamesa's business. In July 2013, Italian developer Veronagest awarded a 234MW O&M deal to Gamesa to service 181 turbines for ten years.
In June this year, Gamesa was handed a 116MW five-year O&M deal by Terna Energy to service its turbines in Poland and Bulgaria.