A detailed morphometric analysis and scanning electron microscopy of seed coat structure of three currently recognised subspecies of the endemic amphi-Adriatic Dianthus ciliatus (Caryophyllaceae) was carried out for the first time. Petal limb shape and denticulation, the woody base of the plant, epicalyx scale’s length and height of the epicalyx turned out to be the most informative characters in distinguishing the investigated populations of D. ciliatus. Based on significant differences in morphological characters, a new identification key is offered. The names D. ciliatus, D. ciliatus var. cymosus, D. dalmaticus, D. medunensis, and D. racemosus are here lectotypified.