Elvis pitched against undisclosed agencies and will now be responsible for on and off trade activation, which will run across pubs and bars as well as in off-licences.
Below-the-line activity will include shopper marketing and promotional activity.
The agency will also work with supermarkets and brewers, alongside Magners' current agency partner The Red Brick Road and Glue Isobar.
Magners has not launched a large-scale campaign since April 2010 when the brand created outdoor activity that used the strapline, "It's all gone pear shaped".
The wonky poster was designed to make it appear as though it had been cropped incorrectly, prompting passers-by to look twice.
Elvis and Magners were unavailable for comment.