Priest Jožef Horvat (born 1880 in Velika Narda, died 1932 in Martjanci), a Croat from Burgenland, spent 27 years of his priesthood (1905–1932) in Prekmurje, then part of Hungary, where he learned Prekmurje due to his pastoral work. The article summarizes the most important biographical information and in the central part provides a linguistic analysis of Horvat's manuscript sermons. Two sermons are discussed – the earliest from 1905, written in Prekmurje with pronounced Croatian elements, and a later one, which shows a gradual adaptation to the Slovene literary language. Based on a comparative analysis of phonological, morphological, syntactic and lexical characteristics and a comparison with the Central Slovene template (Žlogar, Duhovni pastir, 1909), the article reveals the development of Horvat's linguistic abilities and his conscious approximation to the Slovene literary norm. The language of his later sermons shows a balance between the Prekmurje and Central Slovenian traditions, which testifies to the priest's role as a mediator of Slovenianness in the Pannonian region. The article sheds light on the importance of Horvat's sermons as a source for studying interlingual contacts and the processes of unification of the Slovenian literary language in the first half of the 20th century.