Phonotypes are the typical acoustic and articulatory features of phonemes. In the sound-imitative system of language they are distinguished as a special category. The relationship between sound and meaning, which determines the separation of the sound-imitative lexis into a special subsystem of language, is based on the isomorphic mapping of the physical parameters of these features and objects of extra-linguistic reality (denotatum). This property allows to distinguish phonotypes as minimal meaningful units and, consequently, as constructive units of sound-imitative words. In this paper, phonotypes are regarded as constructive elements in the formation of the artificially constructed lexis; it is shown that the sound-imitative functions of the phonotypes of natural languages are realized in artificially constructed words of fictional languages. The material analyzed includes the lexicons of a priori artificial languages Na’vi (author P. Frommer) and Klingon (author M. Okrand) created for the characters of fictional worlds presented in the Avatar and Star Wars film series. The method of phonosemantic groups (Klimova) and the method of phonosemantic analysis (Voronin) were employed as research methods. In the course of this study, it was found that despite the complete absence of conventional norms in the material under study, the lexis which was identified as sound-imitative repeats the sound-imitative patterns known for natural languages. The study has demonstrated the possibility of finding phonotypes in the structure of artificially constructed words, and the similarity of their iconic functions to those of natural languages. This proves that on the current stage of language development people are sensitive to the sound-imitative aspects of speech sounds: they can operate with phonotype parameters, use them to recognize the meaning of existing sound-imitative words and to create new ones. The results, obtained from the previously unexplored material, confirm the validity of defining the phonotype as the basic sound-imitative unit of language.