The objective of this study was to develop and test a temporary marking technique to individually identify free-living brown-throated three-toed sloths Bradypus variegatus at the Ecological Station of Caetés, Pernambuco, Brazil. Forty-six sloths of different genders and age classes were used. The ungueal marking consisted of painting the dorsal and lateral areas of the foreclaws with nail polish of various colors. Monitoring was carried out with binoculars and recapture. The technique did not show any adverse effects on the natural and social habits of the individuals or on the claws. The markings lasted for a period of up to 9 months with variations between individuals, lasting a shorter time in young animals. This type of marking has shown to be satisfactory for the identification of free-living animals and may also be used for studying captive and semi-captive sloths.