Little scholarship exists about the extent of musical nationalism in the works of twentieth-century Italian composer Alfredo Casella (1883-1947). Casella’s output, which is divided into three stylistic periods – 1902-1913, 1914-1920, and 1921-1946 – display varying styles and influences, such as an extension of French, German, and Russian romanticism and Schoenbergian atonality. Yet nationalistic expression simultaneously pervades each stylistic period: The first period portrays nationalism through the use of folk material and forms, as does the second, which also uses programmatic elements in an atonal context. The third stylistic period, to which previous scholars have given the most attention, expresses nationalism by alluding to past Italian Baroque and Classical composers and forms. This thesis explores how Casella’s nationalistic tendencies pervade all three stylistic periods and evolved over the course of his career, culminating in his third stylistic period. A close reading of Casella’s own writings – which will explore how his ideologies reflected the political and cultural views in Italy at the time – and score analysis of representative works from each period will reveal in Casella’s works “a music unquestionably Italian in idiom" (Alfredo Casella, 21+26, 41).