The essay presents an unpublished pencil portrait of Jacopo Alessandro Calvi in a private collection, which captures the scientist Eustachio Zanotti in profile. It also proposes to refer to Calvi’s hand the portrait of the same astronomer preserved in the university collections of Palazzo Poggi, on the basis of a comparison with a further oil portrait by him, also in a private collection, which came to us through the painter’s heirs and was painted in pairs with that of Calvi’s father, the spice merchant Giuseppe Maria, a great friend of the scientist. The painting in Palazzo Poggi is in fact currently in search of an authorship, after a past attribution to the name of Giampietro Zanotti, secretary of the Accademia Clementina, father of Eustachio as well as master of Jacopo Alessandro himself. The attributive hypothesis therefore widens Calvi’s known activity as a portraitist, to which the painter very rarely devoted himself, but that was very significant in order to document the literary interests cultivated by the young artist, and his academic and Arcadian acquaintances.