Smith has overseen the UK business since it was bought by private equity firm Apollo Management for £1.5 billion earlier this year.
Claire’s operates about 3,300 stores across three continents. Mildenstein’s remit will include the UK division, which also includes stores in the Republic of Ireland, the Netherlands and Belgium.
Mildenstein said: “I’m delighted to be joining such a strong brand and at such an exciting time for the business.”
Smith added: “Paul has a great pedigree, with experience including Costa Coffee and T&S Stores. He will be a great addition to our team as well as valuable support to me as we seek to improve our core business and build on our European base.”
Smith has already strengthened Claire’s management team. In June, he recruited Melanie Haworth to the new role of commercial director to head up the trend and product departments, and buying and merchandising for the UK, the Netherlands and Belgium.