A device (200) for customizing a portable electronic entity (100), that includes: elements for storing a plurality of groups of customization data; elements (280) for communication with a non-rewritable memory (130) of the portable electronic entity, for receiving a first identifier (415) stored in the non-rewritable memory; elements for selecting at least one group of customization data according to the first identifier; and elements (240) for customizing the portable electronic entity according to each selected group of customization data. Preferably, the elements for storing a plurality of groups of customization data are designed so that each group of customization data is associated with a second identifier, the device includes elements for associating a second identifier with the first identifier, and the selection elements are designed in order to select at least one group of data according to the second identifier corresponding to the first identifier.