According to the Mirror, the 34-year-old will bring the success of her own clothing line the store – which caters for sizes 14 to 32 – for the sum of £50,000.
It is reported that Evans has already picked pieces from Gemma's range for the store.
Gemma has enjoyed huge success with her online brand, winning Best Designer at the British Plus-Size Awards in 2013.
A source said: "Philip picked up on Gemma's huge online fan base and sees how well her clothes sell with her army of loyal Twitter fans.
"There aren't many popular curvy female celebs who have such clout, so it's understandable that Evans were keep to snap her up, especially since she's so feisty and confident – which is a strong message they want to get across.
"The campaign in a massive deal for Gemma who has always dreamed of selling her designs in the High Street to the masses."
Starting next month, Gemma will be visiting various Evans stores around the country. The TOWIE star will offer fashion and style tips to customers.
Gemma's own clothing line has become so popular that last year she opened up a second Essex boutique.
It looks set to be a busy few months for Gemma, as she returns to our screens tomorrow night for series 14 of The Only Way Is Essex.