The agency, which currently handles the advertising account for Carlsberg's main brand, secured the business without a pitch.
As well as creating an ongoing marketing communications strategy, Saatchi & Saatchi's first task will be to produce a campaign that will break in May.
The campaign, which will run across TV, cinema and print, will seek to strengthen the brand's position in the UK beer market.
Carlsberg took over the UK marketing and distribution of San Miguel in November last year, stating at the time that it had set aside a "significant budget" to support the brand. The beer was the first brand to move out of the newly merged Scottish & Newcastle and Heineken stables.
Carlsberg also handles the distribution for the Russian beer brand Baltika, the Greek beer Mythos and Gimbergen, a Belgian beer.
Saatchi & Saatchi has handled the UK advertising account for Carlsberg since 1973.