Linklaters held on to second place in the table, acting on 415 deals worth $221.6bn (£107bn), according to research by Thomson Financial.
Headline mandates for A&O’s finance department in recent months include acting for Mizuho Securities on a collateralised debt obligation for Mizuho Bank worth ¥279.9bn (£1.18bn).
Commenting on the rankings, senior A&O finance partner Boyan Wells said there had been signs of recovery after a slowdown caused by the global credit crunch.
He told Legal Week: “For the first six months of the year we were doing about 65 deals a month. Over the last quarter that has slowed down to about 45 month but that there are still a lot of deals being done and the Middle East remains especially busy.”
Arch rival Clifford Chance (CC) clung on to third, advising on 238 deals worth $193bn (£93.3bn), while Sidley Austin remains fourth with 101 deals worth $132bn (£63.8bn).
Sidley retained top spot ahead of A&O in the issuer rankings, advising on 248 deals worth $171bn (£82.6bn). The City giant acted on 103 deals worth a combined $102bn (£49.3bn).
Linklaters climbed one spot since the last issuer rankings to place third, bagging 102 deals worth $82.7bn (£39.9), while CC slipped two positions to fifth.
