This dissertation provides a detailed analysis and study of the manner and extent to which the language of the Old Czech text Zrcadlo člověčieho spasenie influenced the language of its Old Croatian translation Zrcalo člověčaskago spasenja. This translation is one of many Old Czech translations made during the residence of Croatian monks in Prague (Emaus) in the 14th and 15th century, also known as the Emaus residence. This dissertation revises and complements previous research on the same subject, and determines on which levels and to what extent the Old Czech component is present in the language of the Old Croatian text. The corpus for this dissertation consists of the Glagolitic text Zrcalo člověčaskago spasenja from a manuscript known as Zbornik žakna Luke (1445) and the Old Czech texts of Zrcadlo člověčieho spasenie (multiple versions). The Latin text Speculum humanae salvationis is used as an aid and corrective measure. The introduction provides the significance of the Zrcalo člověčaskago spasenja in the context of literary history, its graphic, orthographic, and linguistic characteristics, and compares it with Old Czech variants of the same work. Previous research on the same manuscript is also discussed, as is the historical and socio-linguistic background of Czech-Croatian contacts in the 14th and 15th century, including a revision of previous research on these contacts. The theoretical and methodological part of the paper explains the metatheoretical and theoretical bases of the research, gives insight into the theory of contact linguistics, and explains how it has been applied to the aforementioned corpus, taking into consideration the obstacles and limitations which arise from the fact that the contact in this case was realized through translation. The specificities of the Old Croatian translation are also discussed (multiple language components, the age of the material, etc). Special attention has thus been paid to methodologically significant distinctions (synchrony – diachrony), and the interdisciplinary approach to the text material has been emphasized. The following chapters discuss translation techniques, summarize and comment on prior claims about the influence of the Old Czech language on the language of 14th and 15th century Old Croatian translations, and analyze and scientifically interpret the influence of the Old Czech language on the language of the Old Croatian translation on all linguistic levels. The final step of the analysis is a chapter on the adaptation of Old Czech linguistic features in the Old Croatian language. This analysis is also carried out at all linguistic levels, taking into account both the specificities of the old text material and the fact that the original Old Czech template has not survived. A dictionary of Czech loanwords and semantic loanwords gives information on attestations of the same loanwords in other translations from the Old Czech language made during the Emaus residence. This dissertation also provides the complete translation of the as-of-yet unpublished manuscript Zrcalo člověčaskago spasenja. The results of this research show that the influence of the Old Czech language is present on all linguistic levels, albeit unequally, and that it is not represented to the extent that previous research on the same text had supposed.