London-based Foster + Partners, led by architect Norman Foster, won 17 per cent of the vote in the World Architecture 100 2015, a survey of the world's biggest practices undertaken by architecture website BD.
"To be voted most admired practice by our peers is a great honour," said Foster.
"It is a huge tribute to our talented and hard-working teams with their myriad skills and disciplines, both in our many studios around the world and our base in London, all working towards the common goal of bringing innovative design solutions to create a better built environment."
The firm – which had already named Britain's biggest architecture practice of 2014 – completed an overhaul of London's Imperial War Museum and won a competition to design one of the biggest airports on earth last year.
It ranked seven per cent ahead of second-place runners up, Swiss firm Herzog & de Meuron, who took 10 per cent of the vote, while third place was shared by international firm Gensler and the office of Italian architect Renzo Piano.
BIG, the firm led by Danish architect Bjarke Ingels, was in fifth position, while sixth place was shared between Oslo- and New York-based Snøhetta, Irish office O'Donnell + Tuomey, New York studios SHOP Architects and Rafael Viñoly Architects, and global firms KPF and HOK.