The PR?giant advised on 131 deals worth a total of $224bn (£142bn) in the first three quarters of the year, according to data from Mergermarket.
That gave it a clear lead of $82bn over its nearest rival Joele-Frank Wilkinson Brimmer Katcher, which advised on 62 deals worth £142bn.
But Financial Dynamics advised on 25 more deals than Brunswick, taking it to the top of the global league tables by volume, with 156 deals worth $111bn. Finsbury advised on 64 deals worth $85bn.
Global M&A activity stood at $1,422.9bn for the first three quarters of 2010, according to the report, up 25 per cent from the same period in 2009.