The campaign comprises 1.2 million door-drops plus a mailpack, which will be sent out to 100,000 known chocolate consumers.
Both packs mirror the product's packaging and "snap" open to reveal a money-off coupon and a competition to win a hot-air balloon ride. The competition's data-capture forms will be used to gather information on new consumers.
The packs are designed to encourage trial of Snaps - thin curves of chocolate, which are made for sharing.
The work uses the strapline "Snap them up" on the outside, and "So light, so moreish" on the inside and supports Publicis' above-the-line work, launched last month.
The campaign was written by Sarah Peter and art directed by Katie Ballard.
Rebecca Walsh, from the Cadbury innovation team, said: "Traditionally, consumers looking for nibbles to accompany an informal social gathering have been targeted by savoury products. We saw a real opportunity to introduce a chocolate product that is ideal for sharing on these occasions, hence the launch of Cadbury Snaps."