Iconic Australian brand, Just Jeans, is 42 years of age and to avoid a mid-life crisis, it's found a solution - a gorgeous 21-year-old model.

Plucked from the catwalks of New York, Melbourne beauty Shanina Shaik has been signed exclusively for three years to be the face of the brand.

“I’ve never had billboards this big, this is great," Shaik said.

“To be honest four years ago I didn't think this could ever come along."

Brand ambassadors have become a popular retail trend.

David Jones has Megan and Miranda; Jen, Jess and Kris work for Myer; winner of Australia's Next Top Model, Montana Cox, is signed to Witchery; and Portmans' has former Girlfriend Model Search winner, Abbey Lee Kershaw.

But finding the right ambassador can be tricky.

“Choose the right ambassador you can get benefits for both parties - chose the wrong one and a different story can evolve," Steve Ogden-Barnes from Deakin University said.

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Some of the key players from the former marketing and PR team of David Jones are running the 'Just Group' and are revamping the brand.

Former Australian bowler Shane Warne and supermodel Helena Christensen have both fronted campaigns for Just Jeans but this is the first time the company has signed an ambassador.

Shanina got her start at 15 as a finalist on Girlfriend Magazine’s Model Search. The following year she was crowned runner-up on Make Me a Supermodel.

Her star quickly rose, becoming only the fifth Australian ever to strut the catwalk for Victoria's Secret.

“Victoria's Secret has been a highlight in my career, it was an achievement for me and now that I’m ambassador for Just Jeans it is also a huge achievement again," Shaik said.

The brand, which began as one store selling Just Jeans on Chapel Street in Melbourne in the 1970s, is now well established with 250 stores across Australia and New Zealand. But gaining market share in an ever-increasing and evolving industry is not an easy ask.

Zara, Top Shop, and GAP have landed on our shores and soon we'll have Swedish retail giant H & M.

Retail experts predict some local Aussie brands will get lost in the fast fashion invasion.