Frost will replace John Sheekey who is joining Moneysupermarket.co.uk.
Frost will be responsible for all Nectar brand activity and will oversee customer marketing, partnership marketing, the Nectar website, public relations and strategic planning divisions.
Previously, Frost was as European brand director for Unilever laundry brand Persil.
John Sheekey will remain at Nectar until the end of May to ensure a “smooth transition”.
Nectar managing director, Jan-Pieter Lips, says: “I am delighted to welcome James to Nectar. He brings a strong background in brand marketing, and an enthusiasm for a new challenge. His leadership will enable the team to continue our strategy of making Nectar even more customer-led.
In February, Nectar, which is endorsed by Sainsbury’s and Homebase, overtook Tesco’s Clubcard with more cardholders than its rivals.