Hall is the chief executive of Saatchi & Saatchi New Zealand, but will move to London at the end of March to take up his position.
The move means that the current chief executive, Tamara Ingram, becomes the executive chairman, from which position she can maintain her close links with the network's Procter & Gamble client. She is also expected to focus on the agency's new-business effort.
Hall will report to Ingram and work with the executive creative director, Dave Droga, and the executive planning director, Kevin Dundas. There are no plans yet for a deputy for Hall, although this has not been ruled out.
Hall, who has worked for Saatchis for ten years, only became the chief executive of the network's New Zealand outfit in May 2000, and was the managing director of its Wellington office.
He joins the London office as the network copes with two major issues: the loss of the Hewlett Packard global account, which was consolidated into Publicis in November last year, and the new profit-related pay structure introduced as Procter & Gamble phases out its commission-based renumeration.
Picked for his track record within the network, Hall's creative strategy and his experience with big clients such as P&G were also key factors for his appointment, according to Ingram.
She said that no-one from outside Saatchis had been considered for the job: 'We only looked at the best candidate - James.'
The chairman in Europe and the Middle East, Derek Bowman, said: 'Tamara has been instrumental in helping to grow the London agency and I'm delighted that James is joining us in the UK - he has an outstanding record.'
Hall said: 'The London agency represents the heart of the brand - it's where it all started - and I feel privileged to be a part of such a driven team.'
Hall is the latest of a string of Antipodean executives at the network to take top roles. Droga, Peter Cullinane, the executive vice-president worldwide, and the worldwide creative director, Bob Isherwood, all come from Australia. The worldwide chief executive, Kevin Roberts, is from the UK but has lived in New Zealand.