In the first half of the nineteenth century, the seigniory of Šoštanj was also owned by the noble family Del-Negro. The article examines its origin, ramification, and widespread presence in the Šalek Valley and the Celje area during the eighteenth and the nineteenth centuries, as well as its subsequent destiny that brought the now only existing family branch to Khislstein Castle in Kranj and then to the territory of present-day Austria. Particular attention is paid to the question concerning the noble status of the Del-Negros. Franz Del-Negro, whom Emperor Franz II granted the rank of nobility in 1803, invoked his family’s Venetian noble status, which he first had to clearly demonstrate. Another problem was presented by the fact that Franz Del-Negro initially did not use this surname and appeared in earlier sources as Franz Schwarz.