The survey asked 2,318 British women to name their favourite fashionable royal, and the Australia-born beauty came out on top, narrowly followed by William's wife.
Mary, a mum-of-four, has long been praised for her innate sense of style and her elegant wardrobe. Indeed, towards the start of her pregnancy, Kate took a leaf out of the Princess' book and stepped out wearing a teal coat previously worn by the Scandinavian royal.
Since then there have been a number of comparison made between the two style icons — from their sophisticated wardrobes to their fairytale love stories, which transformed them both from commoners to beloved royals.
In the poll, Mary secured 68 per cent of the total vote, with Kate getting 67 per cent. Third place went to Jordan's beautiful Queen Rania who received 61 per cent.
Spain's elegant Crown Princess Letizia and newlywed Madeleine, Princess of Sweden, came in fourth and fifth with 59 per cent and 56 per cent respectively.
Madeleine's older sister, Crown Princess Victoria was named in seventh place (47 per cent) coming in just behind Charlene of Monaco who received 52 per cent.
Rounding up the top ten were Zara Philips, Queen Maxima of the Netherlands and Mette-Marit, Crown Princess of Norway.
Missing out on the list were Princess Mathilde of Belgium (22 per cent), Princess Beatrice (five per cent) and her younger sister Princess Eugenie (three per cent).
Asked who they considered the most stylish royal of all time, the British women surveyed overwhelmingly voted for Princess Diana, who won with 82 per cent.
More than half said they would try a new look or designer if they saw a royal wearing the item in question (62 per cent), and 67 per cent said they looked to royalty from across the world for fashion trends and ideas.
Speaking about the poll, Mark Pearson, Chairman of MyVoucherCodes.co.uk, said, "I was genuinely surprised by the results, as I think that many would assume that everyone's favourite royal style icon would be Kate.
"Judging by the results, its seems that Kate has a bit of competition, in the form of Mary, Crown Princess of Denmark; lovingly nicknamed the Kate of Scandinavia.
"As both women are incredibly stylish, with Mary opting regularly for Malene Birger and Kate wearing anything from Topshop, Hobbs and even L.K. Bennett shoes, it's no wonder that the two women were really popular with the British public."
The Top Ten Most Fashionable Royals
1. Mary, Crown Princess of Denmark - 68%
2. Catherine, Duchess of Cambridge - 67%
3. Queen Rania of Jordan - 61%
4. Letizia, Princess of Asturias - 59%
5. Madeleine, Princess of Sweden - 56%
6. Charlene, Princess of Monaco - 52%
7. Victoria, Crown Princess of Sweden - 47%
8. Zara Philips - 45%
9. Queen Maxima of the Netherlands - 38%
10. Mette-Marit, Crown Princess of Norway - 33%