Tayburn, which beat three other firms to win the brief, will also develop new packaging, an updated website and a suite of point of sale material for the brand.
Chewits mascot Chewie, who has adorned its packs since the sweets hit the shelves in 1965, will be redrawn to appeal to both children and parents.
Joy McCallum, account director at Tayburn, said: "Part of the brief was to redraw Chewie who had become dated and looked too young for today's target audience, so we're looking at making him a little older, and bringing him back with a positive atti-chewed!
"He really needed to be integral to the brand and packaging and not just an 'add on'. The use of mascots in the children's market, however, can be very difficult.
"They have to be relevant and compelling enough to form a relationship with their target audience while respecting the role of parents, so it's a fine balance between communicating responsibly and ensuring he looks great."
The first packs will be rolled out in April 2009, featuring ice-cream flavours, brought back by popular demand following a petition on .
The sweets have been a UK favourite for many years but have recently lost market share to rivals after Chewits manufacturer Leaf closed down a factory in Southport two years ago, which hampered distribution logistics.
The redesign will be aimed at re-engaging the tween market.
Tim Boote, UK marketing manager of Leaf, said: "We were looking for an agency who understands the retail market and what makes consumers and customers tick.
"Tayburn has an impressive track record in the packaging sector and it was this experience, along with tangible evidence that its packaging design works right through to the bottom line, which proved the deciding factor in selecting Tayburn as our preferred creative agency."