The agency won the account after a competitive pitch, which was handled by the AAR.
Candi, which has a client list including Polaroid, Morrisons and Kinder, will be responsible for building Whitbread's restaurant brands through social media and by redesigning each brand's website. The brief does not include digital advertising for the Whitbread-owned Premier Inn hotels or Costa Coffee chain.
Whitbread is looking to support its restaurants following positive recent results, which saw its restaurant chains attract 5.2 per cent more customers between April and June than in the same period the previous year.
The company is to invest an additional £8 million in marketing its hotel and restaurants this financial year, alongside a further expansion in the Premier Inn estate.
Premier Inn's advertising is handled by Rainey Kelly Campbell Roalfe/Y&R and stars Lenny Henry.
In March, Whitbread named the easyJet chief executive, Andy Harrison, as its new CEO. He replaces the current chief executive, Alan Parker, who will retire in November. Harrison will be responsible for growing Whitbread in the UK, and developing its international presence through Premier Inn.