The agency was appointed after a four-way pitch. It has created a programme called "Kreme of the Krop", which will recognise good customer service among the doughnut chain's employees as well as identifying areas that need improvement.
It will also motivate workers to inform customers about what the company described as the "Krispy Kreme Experience". Employees will be rewarded for giving customers a "magic moment".
Retail Eyes will visit Krispy Kreme's 27 locations in the UK on a monthly basis to carry out the programme.
It is the first time Krispy Kreme has used mystery shoppers in the UK.
Judith Denby, marketing director for Krispy Kreme UK, said: "We were attracted to Retail Eyes by the nature of their company culture and their open-mindedness in setting goals for the programme."
Retail Eyes also works for retailers including WH Smith, Subway and HMV.
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