The agency was appointed without a formal pitch and will now be charged with developing creative work for Holsten Pils and the other Holsten brands in the portfolio.
Its debut offering is expected to break in May and will take the form of a national outdoor campaign.
It is believed the work will continue to push the brand's superior quality credentials.
The Fallon managing partner, Michael Wall, said: "Holsten Pils has always competed with brains rather than brawn; we'll look to continue that tradition."
TBWA resigned the account back in January, bringing the curtain down on a fruitful 19-year relationship. The agency claimed it could no longer afford to run the business at a discounted rate.
Falling sales have meant Holsten's advertising spend had slipped to less than £1 million.
Holsten's parent company, Holsten Brauerei, is in the process of completing a takeover bid from the Danish brewer Carlsberg Tetley.
Ben Peters, the marketing director for Holsten UK, said: "I believe passionately that compelling advertising has a key part to play in the long-term future of our brands.
"It was important to Holsten UK that we found a partner who we could trust to continue to develop our brands."