Rome, Ancona, Bologna, Milan and Puria di Valsolda are the places where Pellegrino Tibaldi worked in the years preceding his activity in Milan in the hire of Carlo Borromeo, starting from 1564. In the artist's correspondence with the latter, mention is made of one of the projects in Rome on which Tibaldi was involved during those months: the execution of one of the frescoes in the Sala Regia in the Vatican. The painting remained unfinished, though it is documented by two drawings that have never before been included in the corpus of Pellegrino's works. The present article is the occasion for reconsidering the authorship of these two sheets and, more in general, Tibaldi's achievements during the troubled times that characterized the work projects at the Vatican under the papacy of Pius IV.