We present here the combination of in situ non invasive techniques to investigate a precious 15th century illuminated manuscript of Petrarch’s work, De remediis utriusque fortunae held in the Méjanes library in Aix-en-Provence (France). X-Ray fluorescence spectroscopy, mapping and point analysis, and visible reflectance hyperspectral imaging allow an unprecedented analysis of this manuscript. They provide new clues for its attribution by revealing a partly hidden coat of arms and describing the illuminator’s palette and techniques in detail. We reveal the identity of the first possessor of this manuscript, Tanguy IV du Châtel, known as a 15th century bibliophile close to Louis XI. This information is a further element contributing to the attribution of the richly illuminated folio 6 of this manuscript to François Le Barbier. Pigments and dyes used for this folio have been investigated with particular emphasis on the study of the superimposed colours thus providing a better understanding of the artist’s technique and know-how.