The agency won the account, which has a media budget of more than £5 million, after a competitive pitch organised by Creativebrief. BJL was the incumbent on the account and re-pitched for the business.
Betfred and Brothers and Sisters will start working together immediately to produce a multi-channel national advertising campaign.
The first campaign will launch later this year, in time for the Barclays Premier League football season, which starts in August.
Brothers and Sisters has been asked to build the brand, integrate Betfred’s websites with its stores and broaden gambling’s appeal.
Rakesh Chablani, managing director for Petfre, the owner of Betfred, said: "We face challenging times ahead in an ever-increasing competitive marketplace. Brothers and Sisters showed us a concept that I believe will tackle those challenges head on, giving us the stand out we need."
BJL's most recent work for Betfred used the strapline, "You’ll love a bit of Betfred" and showed a bored man in a supermarket become the centre of a mini-carnival when he starts to make bets on his smartphone.
Brothers and Sisters has also promoted Jonty Harbinson to be head of design. He has worked at the agency for the past 18 months after running his own gallery and creative studio, and working at agencies including Y&R, HKLM and Actuate.