A crucial witness in the transmission of Dante’s epistles is manuscript Vat. Pal. lat. 1729, containing Petrarch’s Bucolicum carmen, the De monarchia and nine of Dante’s epistles, seven of which are attested by this witness only. Compiled around 1394, the manuscript belonged to Francesco Piendibeni, a cultivated humanist born in Montepulciano. Through an extended inquiry, which includes two other manuscripts from Piendibeni’s library (Vat. lat. 2940 and Par. lat. 8027), this paper puts forward a new evaluation of this copy of Dante’s letters.