Otto Jespersen (1860-1943) was a Danish linguist, best known for his studies of English, of phonetics and of general linguistics. In my paper, I introduce a lesser-known side of Jespersen, i.e. as an Italianist and a Romanist. A special focus is on how he deals with the passive tenses in Romance languages, in particular Italian and French. Drawing on the theory developed by the German Romanist Friedrich Diez (1794-1876), who notably differentiated between perfective and imperfective verbs, and subsequently connecting this differentiation to the general discussion of aspect and Aktionsart around 1900, Jespersen in a few pages elaborates a rather advanced analysis of the passive tenses in the Romance (and some other) languages. I suggest that Jespersen’s statement forestalls an important part of the description of the passive tenses in Italian elaborated by the Danish Italianist (and Romanist) Jørgen Schmitt Jensen (1931-2004) and published in a comprehensive Italian grammar (1990). I further propose that even though Jespersen’s text probably is not a direct source for Schmitt Jensen, it helps understanding the general frame of the latter’s presentation of the subject. Finally, I claim that the relevant pages in Jespersen (1924) are interesting concerning the historiography of the concept of Aktionsart.