The subject of master’s thesis is formal and harmonic analysis of Poljica’s folk mass by Boris Papandopulo, one of the most prolific Croatian composers. The above-mentioned piece was preserved in manuscript. Mass is the central service of the Catholic Church, in which the variable and invariable parts of the Mass are sung. Poljica’s folk mass is a six-movement piece for mixed choir and organ, composed to the text of the entire Mass ordinary. Arised on the foundations of Poljica’s church heritage, it evokes the chant and simplicity of the Dalmatian folk song. But, on the other hand, a free formal arrangement of parts, tonal instability and indeterminacy, frequent changes of temporary tonal centers (passing modulations) and modulations into relative and distant tonalities, mode interpolations and neo-Baroque features, testify to the period in which the work was created. Combining the traditional with the contemporary aspirations of European music of the 20 th century, Papandopulo once again proved himself as a composer who successfully integrates different musical styles.