The pressure to slim down is one that many brides face before their weddings.
Watson is a size 14, which is the average customer size for David's Bridal, Glamour reported.
She features in some beautiful snaps that were captured in London, as the designer expands into the U.K.
"I'm so proud to be part of an ad campaign that helps all women celebrate such an exciting milestone in our lives and it's really been an honour to work with a brand that sees the beauty in women of all shapes and sizes," Watson told TODAY.
David's Bridal CCO Trevor Lunn told BuzzFeed that it was important for the company to reflect the diversity of its customers in its campaign.
“It wasn’t that this season was precisely the right time to feature a size 14 model — it’s something we should have been doing all along," he said.
It's not the first time that David's Bridal has used a curvy model in a campaign.
Last year, it featured size 14 model Candice Huffine, who was also photographed for the most recent Pirelli calendar.
But neither are just models. They're also body-image activists who have spoken out on the importance of self-acceptance.
"It's extremely important to accept and love your body, this is why it's so important to have body diversity in the fashion industry," Watson said in a Popsugar story from last year.
"The message should be that all different sizes and shapes are beautiful."
Here are more photos of Mercy Watson, from her Instagram:
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