The two companies will form a 50-50 joint venture called Nokia Siemens Networks, with predicted sales of €16bn and cost savings of €1.5bn euros a year by 2010.
The new company will employ 60,000 people and is expected to be up and running by January next year.
London M&A partner Jonathan Coppin leads the Shearman & Sterling team advising Nokia, which includes partners Iain Scoon and Ian Nisse.
Clifford Chance partners Peter Charlton and Joel Ziff are advising the Siemens in-house legal team.
Dr Lutz Englisch, head of the M&A transaction group at Siemens, and Nokia general counsel Carl Belding, along with M&A director Susanne Mattsson are the key in-house lawyers on the transaction
Faith Dickson of Sackers is providing pensions advice.