BMP was appointed to the advertising brief following a pitch against agencies including Saatchi & Saatchi, Bates UK, Walsh Trott Chick Smith and M&C Saatchi.
H Samuel parted ways with its previous agency, Maher Bird Associates, despite appointing it only last July in a pitch handled by Haystack Group.
The then-incumbent, RPM3, did not repitch for the business.
The brand has not advertised on television for more than five years, although it is expected to return to screens with BMP. Maher Bird was briefed to develop a television campaign for the jeweller, but it was never broadcast.
With the appointment, its parent company Signet is aiming to boost H Samuel's profile in a mass-market audience, while also positioning it as more of a luxury brand than it has been perceived as in the past.
"H Samuel is trying to create a destination lifestyle brand for its stores," Ross Barr, the joint chief executive at BMP, explained. "The experience we have garnered from working with clients such as Heal's, Harvey Nichols and Miss Selfridge is what H Samuel is looking for."
Signet is the world's largest jewellery chain, owning more than 1,600 stores. They comprise more than 420 H Samuel shops and 180 Ernest Jones outlets and Leslie Davis stores in the UK.
The repositioning comes as the retailer faces an increasingly competitive market in which to differentiate its product offering. The likes of Argos and Asda threaten the budget end of the jewellery market, and the diamond giant De Beers has launched a chain of shops in a joint venture with the fashion company LVMH.
Signet used to be known as Ratners, but it was renamed in 1993 after the massive losses sustained when the chairman at the time, Gerald Ratner, infamously announced that some of the company's products were "crap" that sold for less than the price of a prawn sandwich.