Abstract: A pacifier with a dust-free-cap comprises a base having a through hole defined therethrough, a nipple partially inserted through the base and a holder partially inserted into the nipple. Within the base, there is provided with a first wall, a second wall having a length longer than the first wall, an indentation defined in a face defining the second wall and a pair of cutouts diametrically opposed to each other. The nipple has a flange integrally formed and abutting the rim of the first wall when the nipple is partially inserted into the through hole of the base. The holder consists of a post having a plurality of annular rings formed therearound, a positioning ring integrally formed with the post, a key extending out from a periphery of the positioning ring and a loop integrally formed with the positioning ring. When the pacifier is assembled, the nipple is able to be securely received within the cap to protect the nipple from contamination by the ambient air.